PRODUCTION OF VALUABLE PRODUCTS FROM DIFFERENT WASTES

6.4.1 SINGLE CELL PROTEIN (SCP)

SCP refers to the dried cells of microorganisms including algae, fungi, yeast, and bacteria which easily grow on waste substrates, rich in carbon (Ware,

  • 1977). The increasing demand of protein is one of the major challenges, and meeting the protein demand will be a major concern in poor and developing countries in near future. SCP can be extracted by cultivating microbial biomass on different biodegradable wastes, which can be used as protein supplement and substitute of traditional protein source in human foods or animal feeds. Despite the name SCP, protein is not only one component of microbial cell, which also contains carbohydrates, lipids, vitamins, and minerals (Litchfield, 1983). Jamel et al. (2008) stated that SCP contains a significant amount of phosphorous and potassium. However, nutritional quality of SCP varies with microorganisms used, method of harvesting, drying, and processing to be used as food (Bhalla et al., 2007).
  • 6.4.1.1 MICROORGANISMS USED IN SCP PRODUCTION

Fungi, algae, yeast, and bacteria are found to use in the production of SCP. Filamentous fungi are ease to harvest but exerts low amount of protein and retard growth rate. Algae protein is comparable, and in many cases protein quality is higher compared to traditional plant sources. Several studies revealed that two major species, the unicellular green alga, Chlo- rella, and filamentous blue-green alga, Spirulina are the most cultivated for SCP (Raja et al., 2008). Algae poses several disadvantages including concentrate heavy metals, higher cellulose content, and higher production cost with technical difficulties. In addition, the celluloid cell wall of algae remains indigestible in humans and other non-ruminants Extraction of SCP from algae is still complex process (Rasoul-Amini et al., 2009). However, yeast is more suitable for the production of SCP compared to bacteria, mold, and algae (Nigam, 2000). Not only higher nitrogen content in yeast, but also larger size, higher lysine, lower nucleic acid and ability to grow in acidic environment are major advantages to use yeast for the production of SCP (Nasseri et al., 2011). Different species of algae, fungi.

yeasts, and bacteria used in the production of SCP in commercial-scale are given in Table 6.3.

TABLE 6.3 Microorganism and Substrates Used in the Production of Single Cell Protein

Microorganism

Scientific Name

Substrate

Bacteria

Aeromonas hydrophila

Lactose

Aeromonas delvacuate

n-Alkanes

Acinetobacter calcoaceticus

Ethanol

Bacillus megaterium

Non-protein nitrogenous compounds

Bacillus subtilis

Cellulose, hemicellulose

Cellulomonas sp.

Flavobacterium sp.

Thermomonospora fusca

Lactobacillus sp.

Glucose, amylose, maltose

Methylomonas methylotrophus

Methanol

Methylomonas clara

Uric acid and non-protein

Pseudomonas fluorescens

Nitrogenous compounds

Rhodopseudomonas capsulata

Glucose

Fungi

Aspergillus fumigatus

Maltose, glucose

Aspergillus niger

Cellulose, hemicellulose

Aspergillus oiyzae

Cephalosporium eichhomiae

Chaetomium cellulolyticum

Penecillum cydopium

Glucose, lactose, galactose

Rhizopus chinensis

Glucose, maltose

Scytalidium acidophilum

Cellulose, pentose

Trichodenna viridae

Tricliodenna alva

Yeast

Amoco torula

Ethanol

Candida tropicalis

Maltose, glucose

Candida itilis

Glucose

Candida novellas

n-Alkanes

Candida intermedia

Lactose

Saccharomyces cerevisiae

Lactose, pentose, maltose

Algae

Chlorella pyrenoidosa Chlorella sorokiniana Chondrus crispus Scenedesmus sp. Spirulina sp. Porphyrium sp.

Carbon dioxide through photosynthesis

Source: Bhalla et al., 2007.

6.4.1.2 SCP PRODUCTION FROM WASTES

Agricultural and industrial waste as a source of hydrocarbon, nitrogenous compounds, polysaccharides, and slaughterhouse waste (horn, feather, nail, and hair) as fibrous protein have been studied for SCP production (Azzam, 1992; Zubi, 2005). Agricultural waste has great potentiality as substrate for bioconversion into protein. Cellulose is attractive substrate compared to other constituents of agricultural waste. In nature, cellulose is found in matrix form with hemicellulose and lignin and because of this, pretreatment (chemical or enzymatic) is recommended for lignocellulosic substrate where cellulose converts into fermentable sugar (Callihan and Clemmer, 1979). Hongzhang Chen et al. (1999) extracted hemicellulose hydrolysate from wheat straw and used as substrate for the production of SCP (Tricliosporon cutaneum 851). In addition, lignocellulosic agricultural waste, like sugarcane bagasse is an ideal substrate for the production of SCP (Chandel et al., 2012). Samadi et al. (2016) used SSF in a tray bioreactor to produce SCP from sugarcane bagasse using yeast (Saccha- romyces cerexisiae). Results also revealed that carbonate-bicarbonate is the most effective buffer for protein extraction with fermentation time (72 hr), relative humidity (85%) and bioreactor temperature 35°C. The highest protein yield (13.41%) was attained at optimum conditions containing all essential amino acids with some non-essential ones.

The bioconversion of fruit wastes into SCP has the potential to meet the worldwide demand of food protein. The production of SCP from fruit waste may be an effective way to manage organic waste and lower the environmental pollution as well (Barton, 1999). Sufficient amount of carbohydrate and other nutrients make the fruit waste as ideal substr ate for growth of microorganisms (Adoki, 2008; Yabaya and Ado, 2008). Furthermore, submerged fermentation with Saccharomyces cerevisioe was found effective for bioconversion of fruit wastes into SCP, whereas a higher amount of protein (53.4%) from cucumber peel followed by orange peel (30.5%) per 100 g of the substrate was reported by Mondal et al. (2012). Dhanasekaran et al. (2011) used two strains of yeast namely, Saccharomyces cerexisiae and Candida tropicalis for the bioconversion of pineapple waste into SCP. Results revealed that the highest protein content was attained on 3rd day of fermentation for both of strains. Pineapple waste has been suggested to use as effective substrate for yeasts in the production of protein. In another study, banana was found to be the best substrate for Saccharomyces cere- visiae and followed by rind of pomegranate, apple waste, mango waste and sweet orange peel. Mondal (2006) stated that SCP production depends on both compositions of the substrate and cultural factors.

Extraction of natural pigment, capsanthin from dry red capsicum produces a large amount of capsicum powder (Uquiche et al., 2004). This amount is almost 98.6% of the inputted capsicum, which is being discarded as waste in China because of its hot and pungent flavor. However, this waste contains capsaicin and can be used as substrate by yeast in the production of SCP. Zhao et al. (2010) used four yeast strains for bioconversion of capsicum waste into SCP. Inhibition of cell growth of yeast by capsaicin in the medium (CPM) was not found in this study. However, Candida utilis 1769 was found to be potential for the highest SCP formation.

Molasses is commonly used as animal feed or in alcohol production or discarded as waste. Chemical composition, absence of toxic material, and availability with low cost make the molasses as suitable substrate for the production of SCP (Bekatorou et al., 2006). Though molasses is rich of carbon, but it requires ammonia and phosphorus salt supplementation (Ugalde and Castrillo, 2002).

Several studies identified that Cryptococcus albidus, Lipomyces lipofera, L. starkeyi, Rhodosporidium toruloides, Rhodotorula glutinis, Trichosporon pullulan, and Yarrowia lipolytica (formerly known Candida lipolytica) the most specific oily yeasts for bioconversion of waste produced in oil industry (Li et al., 2008; Ageitos et al., 2011). Wastewaters from olive oil and animal fat treatment industiy have been also studied to produce SCP (Papanikolaou et al., 2001). Begea et al. (2011) used sunflower oil as a carbon source for Candida yeast in the production of biological protein. They suggested that the oil industry waste or oily wastewater of the food industry can be used to produce SCP and reduce environmental pollution as well.

A large amount of slaughterhouse wastes are discarded as waste in Turkey. A study shows that almost 25 tons of waste are discarded per year from a medium-size slaughterhouse. These wastes can be converted into valuable products, like protein or amino acid through bioconversion (Atalo and Gaslie, 1993). Physical and chemical methods can be applied to produce crude hom hydrolysate (CHH), which is a suitable substrate for the production of SCP. Kurbanoulu (2001) conducted an experiment to produce SCP from CHH by using Candida utilis NRRL Y-900. Extracted protein from CHH showed good profile of essential amino acids recommended by FAO.

6.4.2 MUSHROOM

Mushroom is a fruiting body of saprophytic, mycorrhizal, and parasites fungi that belongs to Basidiomycetes or Ascomycetes order. In general, mushroom grows on moist agricultural waste, animal waste and soil of higher organic matter. After identifying the nutritional value of mushroom, it has been started to cultivate commercially. Mushroom cultivation in commercial scale is one of the prominent biotechnological processes for valorizing wastes produced from different sources. On the other hand, higher amount of protein, minerals, phytochemicals with medicinal and pharmacological properties are remarkable reasons of cultivating mushroom (Diego et al., 2011). Recent research works stated that some medicinal attributes of mushroom include antiviral, antibacterial, antiparasitic, antitumor, anti-inflammatory, antihypertension, antidiabetic, antiatherosclerosis, hepatoprotective, and immune-modulating effects (Wasser and Weis, 1999; Wasser, 2002; Daba and Ezeronye, 2003; Paterson, 2006).

Furthermore, ecological advantages of the cultivation of edible mushrooms include efficient utilization of agricultural waste like chicken and horse manure, cereal straw and leaves, sugarcane bagasse. In addition, solid and liquid waste from food, paper, chemical, and pharmaceutical industries can be used to cultivate edible mushrooms. It was reported that more than 2000 edible mushroom species are found around the world. Recently, Renganathan et al. (2008) reported that three mushrooms, namely Agaricus bisporus (white button mushroom), Pleurotus spp. (oyster mushroom), and Volvariella volvacea (Paddy straw mushroom) are commercially cultivated around the world. They also noted that Agaricus bisporus is not cultivated in tropical and sub-tropical regions due to suitable climatic condition. Pleurotus species including P ostreatus, P. sajor-caju, P. pubnonarius, P. eryngii, P cornucopiae, P. tuber-regium, P citrinopileatus, and P flabellatu are common to cultivate, which contain all essential amino acids, minerals (Ca, P, K, Fe, Na) and vitamins C, thiamine, riboflavin, niacin, folic acid and antioxidants (Caglarinnak, 2007; Regula and Siwulski, 2007). This species is also known as oyster mushroom, and found to be capable of utilizing complex organic matters with their extensive enzymatic system (Yalinkilic et al., 1994). In addition, oyster mushroom has probiotic properties and relatively high nutritive value than others; this is because it has been recommended to add in the dietaiy chart for people of all ages (Bemas et al., 2006).

According to a survey, almost 200 billion tons of organic waste is produced annually around the world (Zhang, 2008). The maximum amount of produced waste is inedible to humans and animals, causing enviromnental pollution (Laufenberg et al., 2003). Considerable emphasis has given on the valorization of waste, particularly produced from the agro-food industry (Lai, 2005). However, lignocellulosic waste including cereals straw, rice husks, com husks and cobs, cotton stalks, maize, and sorghum stover, vine primings, sugarcane bagasse, coconut, and banana residues, coffee husk and pulp, seed hulls, peanut shells, sunflower seed hulls, paper waste, wood sawdust can be biologically processed through SSF to valuable and usefiil products (Fan et al., 2000a; Pandey et al., 2000a, b; Webb et al., 2004).

Mushroom cultivation is the most efficient utilization and value-addition through biotransformation of lignocellulosic residues among various applications of SSF (Chiu et al., 2000; Zervakis and Philippoussis, 2000; Chang, 2001, 2006). In several studies, mushroom production through SSF has been noted as biodegr adation and bioremediation of hazardous residue (Perez et al., 2007) and biological detoxification of lignocellulosic residues (Fan et al., 2000b; Pandey et al., 2000c; Soccol and Vandenberghe, 2003). Moreover, Lentinula edodes and Pleurotus sp. are found to be potential in the bioconversion of lignocellulosic residues including wheat straw, cotton wastes, coffee pulp, peanut shells, oilseed hull, wood chips, sawdust, and vine primings (Ragunathan et al., 1996; Campbell and Racjan, 1999; Philippoussis et al., 2000, 2001a, b; Poppe, 2000; Stamets, 2000). It has been reported that chemical compositions of biomass have a great influence on the yield and quality of mushroom (Kues and Liu, 2000; Philippoussis et al., 2001c, 2003; Baldrian and Valaskova, 2008). Several studies showed that apart from physicochemical composition of substrate, strain, and length of incubation play an important role in the production of L. edodes (Sabota, 1996; Chen et al., 2000; Philippoussis et al., 2002, 2003).

Randive (2012) studied on the cultivation of oyster mushroom on paddy and wheat wastes. Nutritional analysis of cultivated mushroom revealed some differences within mushrooms of the same species cultivated on different substrates. According to Philippoussis et al. (2000), cultivation of P. ostreatus, P. eryngii and P. pulmonarius demonstrated a higher colonization rate on wheat straw and cotton waste substrates. They also reported that ratio of cellulose to lignin has a positive correlation with mycelium growth along with yield of P ostreatus, and P. pulmonarius. Interestingly, wheat straw supplemented with cottonseed and soybean cake has proved to enhance the productivity of P ostreatus (Upadhyay et al., 2002; Shah et al., 2004). It is a fact that Hasan et al. (2010) prepared substrates by mixing rice straw, poultry litter, banana leaf midribs, horse dung and lime at different ratio for the cultivation of oyster mushroom (Pleurotus ostreatus) and noted the highest mycelium miming from banana leaf midribs + 10% horse dung + 1% lime.

Cassava is the most consumed food in African countries, and almost 700 million people depend on cassava. As a result, a large quantity of cassava waste is generated after processing, and the maximum amount is tuber peels. Cassava waste is usually used as a goat feed in Africa (Sonnenberg et al., 2014). However, several researchers have focused on the mushroom production from cassava waste. Onuolia et al. (2009) utilized sawdust, oil palm fiber, diy cassava peel, and mixture of these agio-wastes for mushroom cultivation (Pleurotus pulmonarius). Adebayo et al. (2009) prepared substrates by mixing cotton waste and cassava peel for the production of Pleurotus pulmonarius. Results revealed that the yield of Pleurotus pulmonarius from cassava peel was comparatively lower than other substrates due to insufficient nitrogen content (Adebayo et al., 2009; Onuolia et al., 2009). Furthermore, Sonnenberg et al. (2014) used cassava peels and stems with different ratios of rice or wheat bran for cultivation of Pleurotus ostreatus and P pulmonarius. They reported that bran supplementation increased the production of oyster mushroom.

Pineapple is one of the most consumed fruits in the world, which can be processed into juice, squash, jam, jelly, and slice can. As a consequent, a large volume of waste is produced from processing industry (Bresolin et al., 2013). Pineapple waste can be used in human nutrition through bioconversion (Martin et al., 2012). According to Fortkamp and Knob (2014), pineapple peel is nutritionally superior to edible portion because of higher dietaiy fiber and protein content, but it is commonly used as animal feed and in the soil amendment. In a recent work, Souza et al. (2016) cultivated three types of mushroom, namely Pleurotus albidus, Lentinus citrinus, and Pleurotus florida from pineapple waste. In addition, they reported all essential amino acids with no toxic element in cultivated mushrooms. Nwachukwu and Adedokun (2014) conducted a research with king tuber mushroom (Pleurotus tuber-regium) cultivation on several wastes including sawdust, mixture of sawdust and paper waste, and mixture of fluted pumpkin stem and paper waste. They reported that the maximum production of king tuber mushroom on mixture of fluted pumpkin stem and paper waste compared with other mixtures. Obodai et al. (2003) used banana leaves, cocoyam peelings and oil-palm pericarp for the production of mushroom. As a pretreatment, dried banana leaves and cocoyam peelings were shocked in water overnight, whereas the oil-palm pericarp was kept in water for 20-30 minute. Two strains of Volvariella volvacea were evaluated, and the highest production of both strains was noted for banana leaves.

Lakshmi and Somaraj (2014) conducted an experiment to eliminate seafood waste through mushroom cultivation (Pleurotus flabelJatus) in laboratory condition. They mixed cooked fish waste with agro-industrial wastes, such as sugarcane bagasse, woodchips, and pith at the ratio of (1:1) and allowed to decompose for 15 days. Interestingly, Chang, and Miles (1993) stated that the utilization of liquid inoculum could reduce the production cost and make the mushroom cultivation process easier. Furthermore, Friel, and McLoughlin (2000) stated that instead of solid inoculum, liquid inoculum could be directly used as substrate to cultivate mushroom. Silveira et al. (2008) cultivated Pleurotus ostreatus in banana straw using liquid inoculum and compared with the results of using solid medium. In addition, they mixed 5% rice bran with dried banana straw powder for using as substrate in the production of Pleurotus ostreatus.

 
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