Production of carbohydrate enrich microalgal biomass as a bioenergy feedstock

Microalgal biomass is considered as a propitious feedstock for bioenergy generation. The present research work aimed to maximize the biomass and carbohydrate productivity of Scenedesmus obliquus UTEX 393 by optimizing physico-chemical parameters using single and multi-parameter optimization strategies. Individual and interactive effects of different parameters (temperature, pH, carbon source concentration and nitrogen source concentration) were investigated. Multi-response optimization study resulted in maximum biomass and carbohydrate productivity of 491 mg L−1 d−1and 270 mg L−1 d−1, respectively at the initial pH 6.69, temperature 27.65 °C, glucose concentration 3.33 g L−1 and urea concentration 126.77 mg L−1. Effect of photobioreactor configuration on biomass and carbohydrate production was also investigated. The biomass and carbohydrate productivity were enhanced to 560 mg L−1d−1 and 309 mg L−1 d−1, respectively using airlift photobioreactor. In a biorefinery framework, before subjecting the biomass for fermentative biohydrogen production, the lipid present (22.6% w/w) in the microalgae was extracted and transesterified for biodiesel production. The potentiality of defatted microalgal biomass (rich in carbohydrate) as a substrate for the dark fermentation process was evaluated using acidogenic mixed consortia. Cumulative hydrogen production of 68.9 mL g−1 DCW was achieved, which suggested the suitability of deoiled algal biomass as a biohydrogen feedstock.