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BIOCONVERSION AND BIOREMEDIATION OF WASTES FROM DIFFERENT SOURCES

6.3.1 AGRICULTURAL WASTES

Agricultural sector produces huge amount of lignocellulosic residues (stalk, stem, root, leaves, stover, groundnut shell, groundnut straw, and bagasse) per year in the world, which consist of cellulose (35-50%), hemicellulose (25-30%) and lignin (25-30%). The main constituent of cellulose is glucose, while hemicellulose is a polymer of five different sugars, including L-arabinose, D-galactose, D-glucose, D-mannose, and D-xylose and organic acids. Lignin is complex, amorphous, and branched polymer of different phenylpropane (Mussatto et al., 2012). Half of the lignocellulosic residue is used as a roofing material, fuel, animal feed, and packing material, whereas the other half is disposed of as waste and of burning. Both burning and disposal of agricultural wastes are causing severe pollution. However, lignocellulosic wastes have a great potential as biomass feedstock and animal feedstuff, but the presence of lignin reduces the digestibility efficiency (Pandey et al., 2007; Graminha et al., 2008).

Lignin is the most abundant organic polymer, which is being degraded by ligninolytic enzymes. Ligninolytic enzymes are a group of extracellular enzymes including peroxidases, laccases, and oxidases (Ruiz-Duenas and Martinez, 2009). It is also capable of hydrolyzing xenobiotic substances such as lignin, hydrocarbons, phenols, carbon tetrachloride aromatics, perchloroethylene, azo dyes, pesticides, humic substances which are discarded into the environment as waste from the industrial area. Disposal of xenobiotic substances is another reason for environmental pollution and threatening to several important organisms (Danzo, 1997). However, ligninolytic enzymes can be used in various sectors, like agricultural, chemical, food, paper, textile, cosmetic, and fuel industry for bioremediation purposes (Rodriguez and Toca, 2006). Production cost of ligninolytic enzymes depends on raw material used in the process. In this perspective, low cost organic wastes are suggested to use as raw material for producing ligninolytic enzymes. Apple pomace (Vendruscolo et al., 2008; Gassara et al., 2010), brewery by-product (Bartolome et al., 2003; Gassara et al.,

2010), municipal, and industrial sludge (Gassara et al., 2010) have been studied as raw material for the production of ligninolytic enzymes. The only study on the production of ligninolytic enzymes using fish processing waste was carried out by Gassara et al. (2010). They used Phanerochaete clirysosporium BKM-F-1767 strain in producing lignin peroxidase, manganese peroxidase and laccase from fish waste. A slight inferior result was revealed compared to apple pomace. In addition, they recommended using other microbial strains for this purpose.

It has been reported that hundreds of fungi are capable of degrading lignocellulosic residues (Kirk, 1983). Soft rot fungi, such as Ascomycetes and fungi inrperfecti can decompose cellulose efficiently, but degrade lignin slowly and incompletely. On the other hand, white rot fungi is found to degrade lignin efficiently by producing ligninolytic enzymes, such as lignin peroxidase, manganese peroxidase and laccase (Isroi et al., 2011). In addition, Trichoderma, and Phanerochaete have been reported as the most efficient lignocellulolytic fungi (Ander and Eriksson, 2006). Most of the bacteria, specially Cytophaga and Sporocytophaga can degrade cellulose under proper conditions, but limited to lignin degr adation. Mesophilic Bacillus both of aerobic and anaerobic, including B. subtilis, B. polymyxa,

B. licheniformis, B. pumilus, B. brevis, B. firmus, B. circulans, B. mega- terium and B. cereus are reported as efficient cellulose and hemicellulose degraders (Ball et al., 1989). In the meantime, several pre-treatments have been suggested for cellulose and lignin degradation as well as yielding fermentable sugar (Chang et al., 2012). In this sense, SSF can be potentially applied for increasing digestibility and producing renewable energy (Lio and Wang, 2012).

6.3.1.1 BIOETHANOL PRODUCTION

Saccharification is an important step in bioethanol production where complex carbohydrates are converted into simple sugars. Therefore, enzymatic hydrolysis shows several advantages, like less toxicity, lower energy consumption, and negligible corrosion than chemical hydrolysis (Sun and Cheng, 2002; Taherzadeh and Karimi, 2007). Then hydrolyzed biomass is subjected to microbial fermentation for ethanol production.

In several studies, simultaneous saccharification and fermentation have been reported better than separate saccharification and fermentation (Bjerre et al., 1996; Balat et al., 2008). At the instance of ethanol production from lignocellulosic waste by hydrolysis or fermentation separately is not cost-effective and associated with growth retardation of yeast due to higher concentration of reducing sugar (Kim et al., 2008). They also suggested using the simultaneous saccharification and fermentation process in which reducing sugar formed by hydrolysis will be converted into ethanol during fermentation. Taherzadeh and Karimi (2007) stated that longer time duration in separate saccharification and fermentation process leads to contamination. In a study, Mutreja et al. (2011) produced ethanol from different agricultural wastes using recombinant cellulase and Saccharomyces cerevisiae in simultaneous saccharification and fermentation process while maximum ethanol yield has been found from Syzygium cumini (Jarnun) at 30°C.

6.3.1.2 BIOCAS PRODUCTION

Biogas is an important renewable energy produced by anaerobic digestion in which organic matter is degraded into reduced methane. In addition, nitrogen, ammonia, hydrogen, and hydrogen sulfide are generated with methane (Angelidaki et al., 2003). Anaerobic digestion for biogas production is divided into four phases, namely hydr olysis, acidogenesis, acetogen- esis, and methanogenesis. At each phase, different facultative or anaerobic bacteria use carbon as their energy source (Gerardi, 2003; Sclmurer et al.,

2009). During hydrolysis, organic matter is degraded into monomers by extracellular hydrolytic enzymes include cellulase, hernicellulase, amylase, lipase, and proteases (Parawira et al., 2008). During acidogenesis, monomers produced in hydrolysis are further degraded into short-chain organic acids, alcohols, hydrogen, ammonia, and carbon dioxide (Schink, 1997;

Schnurer and Jarvis, 2009). In the acetogenic phase, fatty acid with more than two carbon atoms, and alcohols with more than one carbon atom are further degraded into acetic acid, hydrogen, and carbon dioxide by acetogenic microorganisms (Schink. 1997). Methanogenesis is the last stage of biogas production where methanogenic microorganisms use acetate, hydrogen, alcohol, and carbon dioxide for producing methane under strictly anaerobic conditions (Liu and Whitman, 2008).

Biogas production through anaerobic digestion is easier than bioethanol production due to transformation of inhibiting compounds into methane during bioethanol production (Barakat et al., 2014; Benjamin et al., 2014). However, monodigestion of lignocellulosic wastes often results in low methane yield (Sawatdeenamnat et al., 2015). Co-substance, such as animal manure has been suggested to use with lignocellulosic biomass to increase the buffering capacity by supplying macro and micronutrients (Mata-Alvarez et al., 2014). Several researchers have investigated co-digestion, like wheat straw with cattle and chicken manure (Wang et al., 2012), rice straw with kitchen waste and pig manure (Ye et al., 2013) and oat straw with cattle manure (Lehtomaki et al., 2007). It showed a better yield of biogas from lignocellulosic waste.

6.3.2 FRUITS AND VEGETABLES PROCESSING WASTES

In 2013, the total production of fresh fruits and vegetables was 1790 million tons, where 950 million tons from vegetables and 790 million tons from fruits (FAO, 2014). Citrus, mango, apple, grape, pineapple, olive, tomato, and potato are mostly processed fruits and vegetables. In the meantime, processing industry is growing faster, and fruits and vegetables are processed into a variety of products, like jam, jelly, squash, pickle, sauce, and to make available them throughout the year. Thus, a processing plant generates a large fraction of solid and liquid wastes especially at the early stage of processing. Fruit and vegetable processing plants produce about 10-60% solid wastes that include peel, pits, seeds, pomace, trimmings, and spoiled food. In contrast, liquid wastes include pulp, caustic peeling water, wash water, and liquid chemicals (Chakraverty et al., 2003). Generally, open field dumping of organic wastes is practiced, and this is another reason for environmental pollution. However, wastes from the agio-based industry are rich in sugar, and bioremediation or bioconversion is found to be a potential way in managing wastes and reducing environmental pollution (Chakraverty et al., 2003).

Anaerobic digestion can be operated under mesophilic or thermophilic conditions, while thermophilic digestion is found to be more efficient. On the one hand, anaerobic digestion of fruits and vegetable wastes was studied by Das and Mondal (2013) for the production of biogas. On the other hand, predigested waste has been studied as a source of mixed bacteria, while dried fruits and vegetable wastes can be used as substrates in anaerobic digestion. They reported that the biogas from organic wastes through anaerobic digestion is mainly methane. Researcher’s effort has also now focused on co-digestion to improve the biogas production by controlling carbon to nitrogen ratio (Chellapandi, 2004; Gelegenis et al., 2007). Anaerobic co-digestion of orange peel waste and jatropha deoiled cake was studied by Elaiyaraju and Partita (2012) for biogas production. Inhibit acid, like volatile fatty acid is observed when fruit and vegetable waste is digested alone (Jiang et al., 2012), but the amount decreases when it is со-digested with swine feces and mine (Feng et al., 2008). Dahunsi et al. (2015) produced biogas front watermelon peels, pineapple peels, and food wastes through anaerobic co-digestion.

Banana is a widely consumed tropical fruit. Nearly 200 tons of banana peel is produced daily in Thailand, and a small fraction of it is used as feed while the maximum amount is being rotted (Pangnakom, 2006). In a study, Sang et al. (2006) noted that nearly 6 million tons of banana stems and leaves and 1.8 million tons of banana peels are discarded annually as waste in China. Interestingly, Zhengyun et al. (2013) conducted a research on biogas production from banana waste (banana stalk and peel), used as a substrate in mesophilic anaerobic fermentation. In this study, the higher biogas production from banana peel was also noted compared to banana stalk. In another research, the production of hydrogen and methane gas through anaerobic digestion was studied by Nathoa et al. (2014). They reported that banana peel is an attractive substrate for producing hydrogen and methane gas through two-phase anaerobic digestion.

Mango is the second most consumed tropical fruit (Joseph and Abolaji, 1997), grown in more than 90 countries with a global production of 26 million tons in 2004 (FAOSTAT, 2004). The edible portion accounts to 33-85%, while peel and kernel are almost 7-24% and 9-40%, respectively (Wu et al., 1993). However, mango peel is not being used commercially, and a large volume of waste is produced in the processing industry, thus contributing to environmental pollution (Berardini et al., 2005). Researchers are looking for economic raw material for lactic acid production, and mango peel has been suggested by several researchers. Recently,

Jawad et al. (2013) conducted a research work on the lactic acid production front mango peel using bio-fermentation. Reddy et al. (2011) used dried mango peel as a substrate for Saccharomyces cerevisiae CFTRI101 in producing ethanol. Direct fermentation of dried mango peel substrate exerted slow fermentation while the addition of yeast extract, peptone, and wheat bran increased the fermentation rate.

In addition, biodegradable organic matter with higher moisture content in vegetable waste facilitates biological treatment through anaerobic digestion (Bouallagui et al., 2003). Limitations of anaerobic digestion include rapid acidification due to lower pH and production of free fatty acids (Bouallagui et al., 2003, 2005). In spite of the fact that aerobic digestion is not preferred for vegetable waste (Landine et al., 1983). Biomethana- tion of vegetable waste was studied by Kameswari et al. (2007). On the other hand, Vehnumgan and Ramanujam (2011) carried out biomethana- tion of vegetable waste under mesophilic conditions by using a fed-batch laboratory-scale reactor. Sagagi et al. (2009) studied on the biogas production from some selected fruits and vegetable waste and revealed that higher biogas production from cow dung (control) followed by fruit waste and lastly, vegetable waste. Jiang et al. (2012) also stated that cattle slurry could be suggested to use as co-substrate with vegetable waste in anaerobic co-digestion.

6.3.3 FISH PROCESSING WASTES

The consumption of fish resources is more than the previous time, and the amount is almost 105.6 million tons, which is 75% of total production around the world while the remaining 34.8 million tons are being wasted (FAO, 2007). Fish processing industries produce a large amount of solid waste (frslr head, eye, viscera, scales, bones, liver, gonads, guts, and some muscle tissues), and liquid waste includes blood and effluent (Awarenet, 2004). In most countries, incineration or dumping of these wastes is common, which causes environmental pollution (Bozzano and Sarda, 2002).

Advantages in biotechnology exploit the production of value-added products from fish industry wastes. Therefore, fish oil with higher polyunsaturated fatty acids is now extracted and integrated into beverages and other food items (Chen et al., 2006; Kim and Mendis, 2006; Zampolli et al., 2006; Rubio-Rodriguez et al., 2010). Several studies also have suggested that fish processing waste may have potential use as a rich source of protein, lipid, and minerals (Toppe et al., 2007; Kacem et al., 2011). Moreover, fish scale and cartilage could be used in producing gelatin for using in food, cosmetic, and medical industry (Blanco et al., 2006; Karim and Bhat, 2009). Gao et al. (2006) stated that a fish viscus is one of the low-cost substrates for the production of lactic acid by lactic acid bacteria. Interestingly, fish wastes are also good substrates for microbial growth in producing a number of important metabolites (Coello et al., 2000; Vazquez et al., 2006,2008). Meanwhile, various strains of bacteria, yeast, and mold have been studied to produce protease and lipase enzymes, having importance in food, textile, chemical, and pharmaceutical industries.

Fishmeal is produced conventionally from fish waste, but the conventional method has not drawn the attention due to excess production cost and indigestibility of conventional fishmeal. However, biological fermentation can be proposed for yielding fishmeal from fish waste. Aspergillus awamori has been suggested to use in the low-cost fermentation process in producing high-quality fish feed from fish waste (Yamamoto et al., 2005).

Afonso and Borquez (2002) could not find any toxic or carcinogenic material in fish processing wastewater unlike other types of effluents, including industrial and municipal effluent. Considering this outcome, fermented effluent from fish processing area has been suggested to use in agriculture. Several studies have focused on the production of liquid from fishery effluent through the fermentation process (Kim and Lee, 2009; Kim et al., 2010; Dao and Kim, 2011). Kim et al. (2010) used five strains namely, Brevibacillus agri, Bacillus cereus, Bacillus lichemformis, and Bre'ibacillus parabrevis in the fermentation of fish waste for producing liquid fertilizer. This liquid fertilizer has the comparable fertilizing ability and proposed to use in hydroponic culture.

Protease is one of the most important enzymes that can be produced from fish waste. Previous studies have stated that Penicillium sp., Serratia marcescens, Streptomyces sp,,Rhi:opus oryzae, Pseudomonas,Bacillus sp. and Vibrio are widely used in protease enzyme production (De Azeredo et al., 2004; Joo and Chang, 2005; Vazquez et al., 2006). Several researchers have stated that wastes from fish processing industry are inexpensive feedstocks having potential for producing protease (Triki-Ellouz et al., 2003; Vazquez et al., 2006; Wang and Yeh, 2006; Haddar et al., 2010). Defatted tuna fish waste was reported to favor higher protease activity by Bacillus cereus (Esakkiraj et al., 2009). They also revealed that fat-free nature of fish waste is a good substrate for microbial species for the production of proteases enzyme. A similar investigation was also observed by Rhizopus oiyzae for lipase production (Ghorbel et al., 2005).

Production of lipase enzyme by various microorganisms including fungi, yeast, and bacteria has been received much attention in modem enzymology (Sharma et al., 2001). Various studies have reported that fish processing waste is economic substrate for producing lipase enzyme. In addition, pre-treatments like physical and chemical treatment are found effective before using fish processing waste as culture media. Effluent from fish waste boiling was found potential to produce lipase enzyme by Saccharomyces xylosus (Ben et al., 2008; Esakkiraj et al., 2010a). Compositions of waste like carbon source, nitrogen source and free fatty acids have great effect on microbial lipase enzyme production. According to Esakkiraj et al. (2010b), higher lipase production from cod liver oil was found by Staphylococcus epidermidis CMST-Pi 1. It has been scientifically proved that well-balanced nutrients in growth media ensure higher microbial lipase production (Ghorbel et al., 2005; Ben et al., 2008).

Chitinolytic enzyme is another important enzyme can be produced from fish processing waste by bacteria, fungi, yeasts, and viruses. Chitinolytic enzyme has drawn an interest in the food and pharmaceutical industry due to various functional activities, including antimicrobial, antifungal, antitumor, and immunoenhancer (Tsai et al., 2000; Wen et al., 2002; Shen et al., 2009). This enzyme also has potential in the production of single-cell protein (Dahiya et al., 2006). Shrimp, shellfish, and crab shell powder are effective substrates for Pseudomonas sp., Bacillus sp., Serratia sp. and Monascus sp. in the production of chitinolytic enzyme (Wang et al., 2002).

6.3.4 POUL TRY PROCESSING AND SLAUGHTERHOUSE WASTES

The increasing consumption of egg, chicken, broiler, and turkey meat due to better nutritional quality than other sources has made the poultry industry an important and growing sector around the world. Processed poultry products are convenient to prepare, and consequently, the meatprocessing industry is growing rapidly (USDA, 2014). Therefore, a large volume of waste is produced daily from the processing industry and slaughterhouse, which causes environmental pollution unless, managed them properly. The major wastes from meat processing industry and slaughterhouse include livestock manner, rumen, feathers, skin, blood, horn, shell, deboning residue, soft meat and dead body. However, a small amount of bone, feather, and eggshell is processed as a source of calcium, phosphorus, and amino acids to make animal feed (Salminen and Rintala, 2002; Lasekan et al., 2013) and rest of waste materials are discarded in the environment.

Several authors have utilized animal fleshing as a substrate in SSF for the production of protease. A high yield of protease production from animal hair was also reported with activated sludge or anaerobically digested sludge (Abraham et al., 2014; Yazid et al., 2016). Feather is a major waste in the poultry industry since it accounts for 8% of total weight and consists of 90% keratin protein (Onifade et al., 1998). Keratin is insoluble structural protein and difficult to degrade because of strong hydrogen bonds as well as hydrophobic interactions among protein chains, and because of this, feather meal becomes low-grade feed. Considering environmental pollution, several countries banned disposal of feather through burning. On the other hand, some microbial enzymes have been extensively investigated to hydrolyze the insoluble keratin into digestible proteins (Komil- lowicz-Kowalska and Bohacz, 2011; Gupta et al., 2013) for producing feedstuffs, fertilizers, and films (Onifade et al., 1998; Gupta and Ramnani, 2006; Jayathilakan et al., 2012).

Therefore, keratinase producing microorganisms having the ability to decompose feather and have been listed as follows: Absidia sp., Altemaria radicina, Aspergillus sp., Doratomyces microsporus, Onygena sp., Stachy- botrys atra, Trichurus spiralis and Rhizomucor sp. (Friedrich et al., 1999), Streptomyces albs, S. fradiae, S. pactum, S. thermoviolaceus (Noval and Nickerson, 1959), S. thermonilrificans (Mohamedin, 1999), Flavobac- terium pennavorans (Yamamura et al., 2002), Bacillus sp., Stenotroph- omonas sp., Bacillus licheniformis and B. pumilus (Nitisinprasert et al., 1999) and Vibrio sp. (Sangali and Brandelli, 2000). Several research works have suggested to use feather hydrolysates for the production of biofuel, fuel pellets for heating (Ichida et al., 2001; Dudynski et al., 2012), and biolrydrogen (Balint et al., 2005).

In general, litter and livestock maimer are used as fertilizer and fish feed. However, litter and manure can be converted into biogas, mainly methane by anaerobic digestion (Salminen and Rintala, 2002). Anaerobic bacteria are found to degrade the litter and chicken manner at a high rate. In a previous study, it was found that anaerobically digested solid poultry waste is rich in nitrogen but potentially phytotoxic (Salminen et al., 2001). They also observed a positive effect of aerobic post-treatment in reducing the phytotoxicity and other inhibitory compounds including organic acids and ammonia produced in anaerobic digestion of solid poultry waste. Budiyono et al. (2011) conducted a research on anaerobic digestion of cattle maimer and liquid rumens for biogas production. Dried rumen content was also studied for producing fed through fermentation with Trichoderma harzianum (Nova, 2000). According to the Environmental Protection Agency (EPA), wastewater from the slaughterhouse and meat processing industry is more harmful to the environment. Likely, slaughterhouse wastewater is found to be feasible in anaerobic digestion (Pozo Del et al., 2000). Seif and Moursy (2001) treated slaughterhouse wastewater by using a laboratory-scale bioreactor. They also suggested that aerobic digestion should be practiced after anaerobic digestion to improve the effluent quality before discharging into the environment.

6.3.5 DAIRY INDUSTRY WASTES

The daily industry is one of the important food industries and regarded as a wet industry because of using large volumes of freshwater for different diverse purposes. Daily plants in varying sizes also discharge a large amount of wastewater than any other food industries. Studies elucidated that production characteristics, and technical cycle of processing line have great impact on the quantity and quality of waste (Table 6.2) discharged from daily processing area (Wildbrett, 2002; Munavalli and Saler, 2009). Almost 2.5-3.0 liters of effluent per liter of processed milk are produced from receiving station to processing area in a large daily plant, which contains fat, casein, lactose, inorganic salts, detergents, and various sanitizers used for cleaning and washing purposes. All of these pollutants can be characterized by Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) (Vidal et al., 2000; Singh et al., 2014). In earlier, physical methods include sedimentation, aeration, flotation, degasification, chlorination, ozonation, neutralization, coagulation, and sorption ion exchange are found to treat industrial wastewater. Partial treatment, higher cost, secondary pollutants generation, higher quantity solids and use of chemical agents are possible limitations of physicochemical methods (Rodrigues et al., 2007).

TABLE 6.2 Compositions of Effluent of a Typical Daily Industry

Specification

Value

pH

7.2

Alkalinity

600 mg/1 as CaC03

Total dissolved solids

1060 mg 1

Suspended solids

760 mg/1

BOD

1240 mg/1

COD

84 mg/1

Total nitrogen

84 mg/1

Phosphorous

11.7 mg/1

Oil and Grease

290 mg/1

Chloride

105 mg/1

Source: Rao and Datta, 1978.

Bioremediation is a process in which living microorganisms or their enzymes are used for the treatment of wastewater. Environment-friendly microorganisms are commonly used in bioremediation, which has proved to be effective in lowering industrial waste (Ojo, 2006). Degradation of organic waste into nonhazardous end products by using naturally occurring microorganisms is more accepted than any other physical methods. The bacteria including Pseudomonas aeruginosa, P fluorescens, Bacillus cereus, B. subtilis, Enterobacter, Streptococcus faecalis, Escherichia coli and the yeasts belonging to Saccharomyces, Candida, and Cryptococcus genus are common in daily wastewater (Madigan et al., 2000).

However, biological treatment is also a cost-effective method for the degradation of daily wastewater. Several studies have suggested that activated sludge process, aerated lagoons, trickling filters, sequencing batch reactor (SBR), upflow anaerobic sludge blanket reactor and anaerobic filters can be used to manage daily and other industrial effluents effectively (Stover and Campana, 2003; Demirel et al., 2005). Porwal et al. (2015) conducted a research by utilizing microbial isolates of activated sludge for the biodegradation of daily effluent. They used the single and mixed culture of yeast isolates (DSI1) and two bacterial isolates (DSI3) obtained from activated daily sludge to treat the effluent. The addition of any single microbial culture to the activated sludge process was found to increase the overall efficiency of the treatment system. Furthermore, the mixed culture has proved to be more effective and beneficial compared to a single culture. A laboratory-scale reactor comprising aeration tank and final clarifier was studied continuously for three months to treat dairy waste using activated sludge. Activated sludge at retention tune of 5 days was found effective with BOD percentage removal efficiency of 95% for daily effluent (Lateef et al., 2013).

6.3.6 CEREAL PROCESSING EFFLUENT

Parboiling process of rice generates almost two liters of effluent per kilo of raw rice. In addition, parboiled rice effluent contains high amount of organic matter as well as nitrogen and phosphorus (Queiroz and Koetz, 1997). Recently, several yeast stains have been used for treating industrial effluent specially for removing phosphorous (Choi and Park, 2003). On the contrary, use of Candida utilis is not encouraged to reduce nitrogen content in parboiled rice effluent (Rodrigues and Koetz, 1996). Bastos et al. (2014) treated parboiling effluent by using cyanobacterium, Aphanothece microscopica Nageli. It was revealed that this bacterium is associated with the production of single-cell protein (SCP) from wastewater. This bacterium usually uses photosynthesis and removes a high amount of nitrogen and organic matter from parboiling rice effluent. Furthermore, Schneid et al. (2004) suggested using Saccharomyces boidardii and Pichia pastoris for treating parboiling rice effluent with the addition of carbon source. De los Santos et al. (2012) evaluated the effectiveness of Pichia pastoris X-33 as bioremediator to reduce organic matter in parboiled rice supplemented with glycerol.

Com is another important cereal for producing starch, gluten, dextrin, glucose, fructose, and com syrup. In addition, corn-based ingredients are very important for food processing, pharmaceuticals, and biochemical industries. According to CRAR (2009), in the period of 2008-2009, the total production of com was 789 million tons throughout the world. Two distinct processes, namely wet-milling and refinery are commonly used while both processes generate huge amount of waste. Ersahin et al. (2007) stated that refinery process produces more effluent than wet milling while wet milling produces effluent with higher COD. On the other hand, the biodegradability of com processing effluent is comparatively high due to rich in protein and starch content (Howgrave-Graham et al., 1994; Ereme- ktar et al., 2002). A three-stage advanced wastewater treatment plant including an EGSB reactor, intermittently aerated activated sludge system and chemical post-treatment unit, was used for treating com processing effluent (Ersahin et al., 2007). In another research, Duran de Bazua et al. (2007) evaluated that both of aerobic and anaerobic processes in a two- stage biological treatment system for the tr eatment of wastewater from a com processing industry manufacturing tortillas.

6.3.7 OIL PROCESSING INDUSTRY EFFL UENT

Waste from the edible oil refining industry is a major concern in several countries around the world. Soybean, groundnut, rapeseed, sunflower, safflower, cottonseed, coconut, mustard, and rice bran are the main sources of edible oil. Oil refining industry produces spent earth as solid and waste- water as liquid waste. In an edible oil refining industry, huge amount of wastewater generated from processing sections including degumming, de-acidification, deodorization, neutralization, equipment cleaning, and floor cleaning (Thompson et al., 1994). Oil refining effluent causes serious environmental problem specially life treating to aquatic animals. Hence, the treatment of oil refining industry waste is essential because of high amount of organic content. Rupani et al. (2010) reported that the treatment of oil refining industry depends on the amount and type of organic matter present in waste stream.

Wastewater of edible oil refining industry can be treated by chemical and biological means. Chemical treatment process combines chemical purchasing cost and production of chemical sludge, whereas biological treatment is convenient and cost-effective. Mkliize et al. (2000) stated that activated sludge and SBR could be used in the biological treatment of oil industry effluent. Interestingly, Aslan et al. (2009) revealed that 95% of BOD in soybean oil refining effluent could be removed by using an activated sludge.

6.3.8 SUGAR MILL EFFLUENT

Sugar industry plays a vital role in the economic development of a country but effluent generated from sugar mill contains high amount of organic matter. According to Baskaran et al. (2009), 110-115 m3 water is required in a sugar mill with a capacity of producing 35,000 kg sugar daily while 87% of water comes out as wastewater. It has been reported that sugar mill effluent causes environmental pollution when discharged into water, consequently, it results in high rate of fish and aquatic animal mortality and various diseases of people when they use for agricultural and domestic purposes (Baruah et al., 1993).

Out of several treatments, bioremediation offers a cheap and environmental friendly alternative for biological degr adation of industrial effluents. In a study, Saranraj and Stella (2012) used Bacillu subtilis, Serratia marcescens and Enterobacter asburiae for treating sugar mill effluent. Bioremediating of sugar mill effluent showed a drastic reduction in organic matter content in terms of COD, TSS, and TDS, heavy metal content, and other physical properties. In addition, Buvaneswari et al. (2013) identified five native bacterial isolates, namely Staphylococcus aureus, Bacillus cereus, Klebsiella pneumoniae, Enterobacter aeruginosa, and Escherichia coli that are capable of bioremediating of sugar mill effluent.

6.3.9 BAKER'S YEAST PRODUCTION EFFL UENT

Baker’s yeast, Saccharomyces cerevisiae is commonly used in the production of bakeiy products. A baker’s yeast industry is important where molasses is used as substrate for the production of Saccharomyces cerevisiae (Catalkaya and Sengul, 2006). The production process includes cultivation, fermentation, separation, rinsing, and pressurized filtration. Fermentation process produces a large volume of wastewater with high amount of organic substances, nitrogen, trimethylglycine, sulfate, and phosphorous content (Blonskaja et al., 2006; Liang et al., 2009).

In an earlier study, Gulmez et al. (1998) studied the feasibility of anaerobic treatment for baker’s yeast industry wastewater. Feasibility was found comparable with the pharmaceutical industry. Kalyuzhnyi et al. (2005) treated the baker’s yeast industry effluent through anaerobic treatment by using an UASB reactor followed by aerobic-anoxic biofilter and coagulation process. Moreover, Krapivina et al. (2007) used anaerobic SBR for treating sulfate-rich baker’s yeast industry effluent.

6.3.10 TANNERY INDUSTRY EFFLUENT

The leather industry is economically important for a country because of increasing demand for leather products in which 65% leather is used in footwear. Nowadays, leather industry uses tanning process due to easier procedure, low cost, light color with greater stability of leather, which generates large volume of wastewater (Jenitta et al., 2013). In the tanning process, huge amount of chromium sulfate Cr(III) and pentachlorophenol (PCP) are used for the conversion of hides and skin into the leather (Ackerley et al., 2004). At least 300 kg of chemicals has been reported to use per ton of hides during the tanning process (Verheijen et al., 1996). It is found that the amount of Сг(Ш) varies from 500 to 7000 ppm and PCP varies from 10 to 90 ppm in tannery effluent which persist longer period in the environment having negative effect on the flora and fauna. Additionally, Cr(III) converts into soluble Cr(VI) during longer persistence in the environment which is toxic and carcinogenic (Ackerley et al., 2004).

Physicochemical methods, such as precipitation with hydroxide, carbonates, and sulfides, adsorption on the activated carbon, use of resins, and membrane separation technique can be applied to remove metals from tannery wastewater, but all of them are expensive (Park et al., 2000). On the contrary, several researchers report that biotransfonnation and biosorptiorr are emerging technologies in which microorganisms are used to transform or to adsorb metal from effluent (Kovacevic et al., 2000; Eddy, 2003). Aerobic digestion of farmery effluent has been reported to reduce the COD and BOD by 60-80% and 95%, respectively (Ganesh et al., 2006). Again, anaerobic digestion produces large amount of biogas by converting the organic pollutants of farmery effluent into a small amount of sludge. Furthermore, chromate reductases are a group of enzymes, which catalyze the reduction of toxic and carcinogenic Cr(VI) to the less soluble and less toxic Cr(III) (Park et al., 2000). Bioremediatiorr can be applied to degrade pollutants in farmery effluent (Mohapatra, 2006; Movahedin et al., 2006). Hence, both intracellular and extracellular enzymes produced by microorganisms are efficient catalysts for byconversion of organic materials in tannery effluent (Nelson and Cox, 2004). Biosorptiorr of chromium from tannery effluent by fungal strain (Aspergillus niger FISH) and bacterial strain (Aci)ietobocter sp. IST3) were studied by Thakur and Srivastava (2011). SEM-EDX analysis revealed that both of fungi and bacterium contained chromium within the cell. In another study, Tolfa da Fontoura et al. (2015) treated farmery wastewater with Scenedesmus sp. The cultivation of microalgae (Scenedesmus sp.) in wastewater of tannery industry was found to be a prominent treatment process. This microalga is also capable of removing of N-NH3, TKN, phosphorus, BOD, and COD up to 80% from effluent.

 
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