AGRICULTURAL BIOMASS AS AN OPTIMIZED CARBON SOURCE
Agricultural biomass is exploited in various bioprocesses by using it as a carbon source. Besides the important enzymes starchy residues have been found to be rich in various components that make them the excellent carbon source in various bioprocesses. Agricultural biomass like Oil cakes, rice bran, soya bean hulls, barley husk, maize are being widely used as optimized carbon sources in many bioprocesses like solid state fermentation (SSF) and submerged fermentation (SMF).
SOLID STATE FERMENTATION (SSF)
This fermentation is earned out in absence of free water. In SSF solid agricultural biomass containing enough moisture like sugarcane bagasse, coffee pulp, oilseed residue which are economical and easily available are used as source of nutrients to support the microbial activities. This solid matrix of agricultural biomass acts as a source of carbon and other nutrients for the metabolism of microbes. The efficiency of SSF is dependent on various factors viz. temperature, aeration, microorganisms, and type of fermenter used (Pandey et al., 2003). The different cultures of microorganisms used in SSF are as:
- • Single pure culture;
- • Mixed identifiable culture;
- • Consortium of mixed indigenous microorganisms.
SSF is a multistep process which is carried out in following steps:
- 1. Substrate selection;
- 2. Pretreatment of substrate either mechanical or chemical;
- 3. Hydrolysis of substrates;
- 4. Fermentation process;
- 5. Downstream processing.
SUBMERGED FERMENTATION (SMF)
This process involves the growth of the microorganisms (mostly fungi) as a suspension in liquid medium in which various nutrients are either dissolved or suspended as a particulate solid. Besides SSF, this process also utilizes agriculture wastes as carbon source. The various substrates that serve as cellu- losic substrate are used as carbon source rather than pure cellulose production thus shows the potential of bringing down the cost of cellulase remarkably.
PRODUCTION OF XYLOOLIGOSACCHRIDES (XOS) FROM AGRICULTURAL WASTE
Biotechnology had played a major role in value addition of agroresidues. One of the major developments in this aspect is transformation of this waste into taste. For this lignocellulosic biomass has gained much attention in the production of nutraceutical compounds known as xylooligosacchrides (XOS) (Collard and Blin, 2014). XOS are the polymers of xylose sugars that are produced from lignocellulosic biomass. This acts as prebiotic and selectively feeds the beneficial nricroflora like Bifidobacteria and Lactobacilli within the gastrointestinal tract (Samanta et al., 2015). The consumption of XOS have been found to induce certain health benefits like immune system stimulation, reduction of blood glucose and cholesterol, increased mineral absorption, and laxation. The sweet taste of XOS has allowed it to be used as artificial sweeteners (Singhania et al., 2017).
With the advancement and development of biotechnological applications, certain approaches are available for the production of XOS. These include:
- 1. Direct Hydrolysis of Substrate: This process is carried out with the help of certain enzymes like hemicellulases and commercial enzymes like Celtic Htec2 to convert lignocellulosic biomass into xylose sugars under mild conditions. The use of commercial enzymes reduces the cost of process and also allows one to simultaneously evaluate the effect of factors on the process through the use of Design expert software (Golshani et al., 2013).
- 2. Autohvdrolysis: This process is carried out under high temperature and pressure which is accommodated by special equipment. During this process, the corrosive chemicals are eliminated (Aachary and Prapulla, 2011).
CONCLUSION AND FUTURE DIRECTIONS
Agricultural biomass is an abundant natural resource that has an immense potential to be used for the welfare of mankind from the generation of electricity to the production of food. There is a need to create awareness among the masses about the toxic effects of direct burning of agricultural biomass as well as the potential of these wastes to be employed for conversion into energy. Although biotechnology had played an important role in mitigating the waste into taste but still more ecofriendly techniques need to get flourished. To accomplish this aspiration, collective global efforts are required.
The special thanks are due to the Research Centre, College of Pharmacy, King Saud University, Riyadh, and Deanship of Scientific Research, King Saud University, Kingdom of Saudi Arabia.