الفهرس 
ACKNOWLEDGMENTOnly 14 pages are availabe for public view
 |  | from | 93 |  |  |
| | | from | 93 | | |
Abstract
In degumming of plant bast fibers (Saleem et al., 2008); the fibers contain gum, which should be eliminated before its use for textile making. The chemical degumming treatment is toxic, polluting, and non-biodegradable. Biotechnological degumming using pectinases with xylanases presents an economic and eco-friendly method (Kapoor et al., 2001).
In Coffee (Murthy and Naidu, 2011) and tea fermentation (Thakur and Gupta, 2012); pectinase treating speed up tea fermentation and as well destroys the foam forming property of instant tea powders by breaking down pectin. They are also used in coffee fermentation to eliminate mucilaginous coat from coffee beans.
Pectinase can depolymerize pectin and then decrease the cationic request of pectin solutions and the filtrate from peroxide bleaching in paper and pulp industry (Reid and Ricard, 2000).
In Animal feed; pectinase is used in the enzyme cocktail, used for the production of animal feeds. This minimizes the feed viscosity, which increases absorption of nutrients, liberates nutrients, either by liberating nutrients blocked by these fibers and reduces faeces or by hydrolysis of non-biodegradable fibers (Hoondal et al., 2002).
Extraction of plant viruses in cases where the virus particle is limited to phloem, alkaline pectinase and cellulase can be applied to release the virus from the tissues to give very pure preparations of the virus (Salazar and Jayasinghe, 1999).
In the case of oil extraction (Najafian et al., 2009); citrus oils as lemon oil can be extracted with pectinases. They break down the emulsifying properties of pectin that interferes with the group of oils from citrus peel extracts. Pectinase also increases pigmentation by extracting extra anthocyanins (Tucker and Woods, 1991).
Pectinase is used in pectic wastewater treatment (Tanabe et al., 1987), Vegetable food processing industries release pectin, containing waste water as a by-product. Pretreatment of this waste water with pectinolytic enzymes facilitate elimination of proteinaceous material and render it favorable for decomposition by activated sludge treatment (Hoondal et al., 2002).
Pectinase finds applications in the production of pectic oligosaccharides as efficient food components as a prebiotic ingredient (Combo et al., 2012; Sabajanes et al., 2012) and liberates of DNA from plants (Rogstad et al., 2001).
1.6. Pectinase production by microorganisms
Microbial enzymes are applied in many environment-friendly and economic processing sectors (Hoondal et al., 2002). Microbes are the preferable source of enzymes as they permit an economical technology with low resource consumption and minimize emission involving no social and political issues, as in the case of animal and plant sources (Dalvi et al., 2007).
Microbially derived pectinases get more use due to their characteristic over plant and animal derived pectinases. The reasons being inexpensive production, easier gene manipulations, faster product recovery, and furthermore microbial enzymes are commonly free of harmful substances.
Pectinases are produced by numerous organisms such as bacteria (Karbassi and Vaughn, 1980), fungi (Aguilar and Huitron, 1990) and yeasts (Gainvors and Belarbi, 1995), bacterial species producing commercial enzymes are always preferred over fungal species because of facility of fermentation process in production and implementation of species improvement techniques(Suneetha and Prathyusha, 2011). Some of the bacterial species producing pectinase are Agrobacterium tumefaciens, Ralstonia solanacearum, Bacteroides thetaiotamicron, and Bacillus sp. (Jayani et al., 2005).
Presently, the pectinolytic enzymes used for industrial applications are produced by the fungi, namely, Aspergillus sp., Aspergillus japonicus, Rhizopus stolonifer, Alternaria mali, Neurospora crassa, Fusarium oxysporum, Penicillium italicum ACIM F-152, and many others (Jayani et al., 2005).
Marine microorganisms have lately emerged as a rich source for the production of industrial enzymes (Chandrasekaran, 1997). Marine bacterial enzymes have various advantages for industrial utilization. Most marine bacterial enzymes are frequently thermotolerant, remaining stable at room temperature for long periods. Also, the optimum activity of marine bacterial enzymes commonly occurs at high salinity, making these enzymes utilizable in many difficult industrial processes, where the concentrated salt solutions used would otherwise prevent many enzymatic transformations (Mohapatra et al., 2003).
1.7. Pectic wastes as microbial activity inducer
Various substrates were considered a good source of pectin that could be extracted by chemical or microbial methods. Pectin acts as the inducer for the production of pectinolytic enzymes by microbial systems. The benefit of using micro-organisms for the production of enzymes is that these are not affected by climatic and seasonal variation, and can be subjected to genetic and environmental manipulations to increase the yield (Bhardwaj and Garg, 2010).
At the present days, commercial pectin is almost exclusively derived from the citrus peel or apple pomace, both by-products from juice industry. Apple pomace contains 10-15% of pectin on a dry matter basis. Citrus peel contains 20-30% (May, 1990). Alternative sources include sugar beet waste from sugar manufacturing, beet pulp a waste product of sugar production from sugar beet also was considered as an origin of pectin that could be bio-extracted more efficiently and economically by microbial methods than chemical methods, sunflower heads (seeds used for edible oil), and mango waste (Maier et al., 1993), onion, lime, lemon, tomato, grapefruit, guava,…etc.
1.8. Statistical design for production medium optimization
Statistical design may be used to know the effect of nutritional conditions on the pectinase activity. Early, optimization of fermentation factors is done by one factor at a time (OFAT) technique by varying one factor and keeping the other factors at a constant level. Also, to screen the most vital variables in a medium when a large number of factors have to be investigated, Plackett-Burman design (Plackett and Burman, 1946) was used to be more efficient to deal with a large number of variables. The Plackett-Burman design deals with factors affecting the objectives were evaluated by application of two- level factorial experiments.
1.9. Immobilization of bacterial cells
Immobilization is a general expression describing a wide variety of the cell or the particle attachment or entrapment (Lopez et al., 1997). It can be utilized in all types of biocatalysts including enzymes, cellular organelles, and animal & plant cells and it considered the means by which cells or enzymes are transformed into heterogeneous catalysts, these immobilized biocatalysts have enormous range of applications not only in the field of biotechnology, but also in pharmaceutical, chemical, environmental, food and biosensor industries (Peinado et al., 2005).
Cell immobilization has been defined as the physical reservation or localization of viable microbial cells to a special defined area of space in such a way as to limit their free migration and show hydrodynamic features which vary from those of the surrounding medium while retaining their catalytic activities for repeated and continuous use (Dervakos and Webb, 1991; Freeman and Lilly, 1998; Covizzi et al., 2007; Amim et al., 2010). Immobilization of microbial cells has received growing attention in the field of waste treatment (Cohen, 2001; Ahmad et al., 2012).Compared with traditional suspension method, the immobilized microorganism technology present a multiplicity of advantages, such as high biomass, high metabolic activity and large resistance to poisonous chemicals (Cai et al., 2011; Liu et al., 2012).
Immobilization of cells containing specific enzymes has further characteristics such as elimination of prolonged and costly procedures for enzymes separation and purification and it is necessary to expand their application by enabling refining of products from reaction mixtures, easy separation and efficient recovery of catalyst (Junter and Jouenne, 2004; Stolarzewicz et al., 2011). In comparing with immobilized enzymes, immobilized cells supply new possibilities since they can be used as natural, water-insoluble carriers of desired enzyme activities (Vojtisek and Jirku, 1983).
Different immobilization types are covalent coupling/cross-linking, entrapment and adsorption, capture behind semi-permeable membrane or encapsulation, (Mallick, 2002). The types of immobilization can be divided as ‘‘passive” (using the natural susceptibility of microorganisms to attach to surfaces-natural or synthetic, and grow on them) as in case of adsorption and ‘‘active” (chemical attachment and gel encapsulation) as in case of entrapment (Cohen, 2001; Moreno-Garrido, 2008).
Entrapment is an irreversible process, where immobilized cells are entrapped in a support matrix this technique creates a conservative barrier around the immobilized microbes, ensuring their prolonged viability during not only processing but also storage. The entrapping agents used are agar, carrageenan, alginate, cellulose and its derivatives, gelatin, collagen, epoxy resin, polyacrylamide, polystyrene, polyester, and polyurethane (Ramakrishna and Prakasham, 1999). The entrapment technique is based on the inclusion of cells within a static network to hold the cells from dispersing into surrounding medium while still allowing penetration of substrate. Entrapment allows high mechanical power but contains some disadvantages, costs of immobilization, cell leakage, propagation limitations, and deactivation during immobilization and scratching of support material during usage , another disadvantage is low loading ability as biocatalysts have to be integrated into the support matrix (Song et al., 2005; Gao et al., 2010; Stolarzewicz et al., 2011).
The adsorption of microorganisms onto porous and inactive support mat.