Paper, Textile and Biopolymers Modification of starch improves its industrial application and enhances its utilization as a substitute for fossil-derived resources. Modified starches are mostly designed for industrial applications, because of the high cost of safety studies needed to certify them by regulatory bodies for food use (Thranathan, 2005). Modified starches find important applications in paper, textile and thermoplastic industries. The paper industry is the main user of modified starch; each tonne of paper requires 55 kg of starch (Tupper, 2000). CS, due to its sterling qualities such as ability to form strong film, clear paste, good water holding capacities and stable viscosity, makes it a good choice for use in paper-making (Cassavabiz, 2005).
Cationic modified starch is widely used in large-scale paper industries to increase tensile fold and bursting strength of the paper (Howard and Jowsey, 1989; Yang et al., 2009). Several research efforts have been made to improve the functionality of cationic starch and to improve the economy of its use in the paper industry by devising processes that do not involve costly drying and heating processes, shorten the reaction time and reduce or eliminate the residual reagents in the final product (Fit and Snyber, 1984; Luo and Fu, 2010). Gao et al. (2012) attempted to improve on the functional properties of cationic modified CS for paper-making. CS was initially pretreated followed by optimization of the reaction parameters for maximum degree of substitution of cationic starch. The results were the improvement in the pasting stability of starch, increase in the surface area of granules and improved reaction process. Lower breakdown values were reported for starch granules, which indicated higher stability when exposed to heat treatment at higher temperatures and mechanical stirring (Ragaee and Abdel-Aal, 2006).
Starch is utilized in three main areas in the textile industry: sizing, finishing and printing. About 80 % of the starch used in textiles is used in sizing. China’s textile industry, which is the largest in the world, relies mostly on modified starch from CS obtained locally and through importation from neighboring cassava-producing countries like Thailand and Indonesia (Wang, 2002). Starch modified by graft polymerization is employed in textiles as a sizing agent during weaving and thickener for printing cotton fabric (Hebeish et al., 1992; Willet, 2009). Witono et al. (2012) optimized graft copolymerization of CS with acrylic acid and observed that the grafting efficiency, temperature, starch concentration and starch to monomer ratio were found to have major influences on the identified parameters.
Biodegradable Plastics Problem of degradation of synthetic polymers by soil microorganisms, which has been causing a serious environmental hazard, led to research for the development of biodegradable plastics (Nakamura et al., 2005). One of the options proposed is the incorporation of natural filler in the polyethylene, which would reduce its mechanical strength and make it porous for subsequent degradation by microorganisms. Several studies have explored the potentials of CS as a filler in synthetic polymers. These include incorporation of CS grafted by radiation with acrylic acid in polyethylene (Kiatkamjornwong et al., 2001), incorporation of native CS in low-density polyethylene and subsequent biodegradation tests in activated sludge (Nakamura et al., 2005) and cassava starch grafted with polystyrene copolymer synthesized using suspension polymerization techniques (Kaewtatip and Tanrattanakul, 2008). They all reported faster degradation and recommended further research into optimization of the processing parameters for subsequent adoption by industry.
Prospective Utilization and Research Starch-albumen powder (SAP) is a composite product of CS and poultry egg white that was developed by Shittu et al. (2010a). The functional properties of the product indicated that it has wide potential as an ingredient for food applications in the fast food, baking and confectionery industries. The product is highly hygroscopic and has the typical type II isotherm. The monolayer moisture capacity ranged between 4.9 and 6.8 g/100 g solid. The paste made from the product showed some pseudo-plastic behavior (Shittu et al, 2015c). However, it is yet to have commercial applications.
A potential product that could be of great importance to the energy industry is the hydrogen gas from CS. Cleanliness of hydrogen, high energy density and recyclability is giving its attention as a potential alternative to fossil fuels (Das and Verziroglu,
2001). Su et al. (2009) studied the potential of producing hydrogen gas from CS as a substrate and compared the hydrogen yield (HY) and production rate (HPR) using different CS concentrations, pretreatment of CS with either gelatinization or enzymatic hydrolysis, under dark, photo and combination of dark and photo fermentation. The study reported that pretreatment with either gelatinization or enzymatic hydrolysis led to HY and HPR with dramatic reduction in delay time and fermentation time. Combination of dark and photo fermentation recorded a significant increase of HY by about 59.70 % from yield in dark fermentation only and increase in energy efficiency to 27.1 % from original 18.6 % in dark fermentation for starch content of 25 g/l. The report concluded that the combination system has great potential for commercial hydrogen production.
Acetone-butanol-ethanol (ABE) is produced biologically through the fermentation of biomass by Clostridium spp. under strict anaerobic condition. This process is important because all products are useful in industry, especially as substitutes for fossil-derived fuels (Jones and Woods, 1986). Butanol is the most valuable of the three, because of its outstanding physical properties such as higher energy content, high boiling points and its compatibility with combustion engines, besides its applications in other industries like food and plastic among others (Jesse et al., 2002; Tran et al., 2010). Tran et al. (2010) investigated the potential of producing ABE from CS using a co-culture of Bacillus subtilis and Clostridium botylicum. The fermentation process was optimized to favor more butanol production. The optimum conditions for enhanced amylase activity and starch utilization was a CS concentration of 40 g/l, yeast extract to NH4NO3 ratio of 265/100. The process is economical and has great industrial application, since there is no need for cost anaerobic pretreatment and the substrate is cheap and readily available.
One of the major problems of large-scale CS production is the high amount of waste (bagasse) generated. This bagasse was reported to contain significant amounts of non-extracted residual starch (40–60 %) (Pandey et al., 2000). Efforts to reduce environmental pollution caused by the waste generated led to research on the prospects of its transformation into industrial by-products. A cardboard-like composite with characteristics similar to the molded fiber packaging from recycled paper was developed by Matsui et al. (2004) from cassava bagasse (CB) mixed with Kraft paper. A potentially high-value all-cassava nano-composite packaging material was developed from CB fibers and a thermoplastic CS matrix by Teixeira et al. (2009). The incorporation of CB cellulose nanofibrils in the thermoplastic CS matrix resulted in a decrease of the CS hydrophilic character and capacity of water uptake, especially for glycerol plasticized samples.