LIPIDS PRODUCTION FROM OLEAGENOUS MICROBES USING AGRICULTURAL RESIDUES AS A FEEDSTOCK

Abstract

Energy crisis, food insecurity, global warming, fossil emissions, and open burning of agricultural residues are growing challenges across the world. Such state of affairs has forced scientists and engineers to introduce green biotechnology for reliable production of biodiesel. Current interest in oil accumulation by oleaginous strains is highly appreciable for converting agricultural residues into lipids as an alternative renewable energy resource. The objectives of present work were to optimize oleaginous microbial growth and to produce lipids through oleaginous fungal strain(s) using agricultural waste as a feedstock. The lipids may further be utilized for bio-energy generation. Chemical pretreatment (acid and base) followed by etherification process was used to synthesize carboxymethyl cellulose (CMC) from lignocellulosic cotton ginning waste (CGW). Fungal growth rate was determined through point inoculation technique. Bligh and Dyer, lipids protocol was preferred method for lipids extraction from dry fungal biomass. Different pH levels i.e. 5.5, 6.0, 6.5, 7.0, & 7.5 were tested to achieve maximum growth of fungal strain. Mean radial growth rate of Fusarium oxysporum was determined for six days on CMC carbon source derived from CGW. Alternaria arborescence, Alternaria alternatae and Asperigillus flavous fungal strains had negative growth response towards CMC energy source. The growth and morphological characteristics of Fusarium oxysporum on different carbon sources (PDA, SDA, CMC-A, and CGW-CMC) were also compared. The maximum colony diameter was 85 mm in response to CGW-CMC after 6 days of incubation period. Optimized growth conditions were 6.5 pH and 28 °C temperature. General morphology of strain in response to energy sources and substrate composition represented velvety surface and color altered from orange to white. On average 36 milligram fungal bio-mass was harvested from 100 mL of fermentation media. Estimated annual production of CGW in Pakistan is 0.3 million tons with 50% cellulose recovery efficiency in the course of acid-base chemical pretreatment. Keeping in view the annual production of agricultural waste, Fusarium oxysporum through enzymatic hydrolysis may produce 540 tons/year of lipids by consuming 0.15 million tons/year of CMC as a growth substrate. Furthermore, 0.15 million tons/year of cellulose may also produce 52500 tons/year of bio-ethanol. The future scope of the study signifies that the cotton waste recovery for bio-fuel production in Pakistan will escort to establish multi-dimensional scientific models and engineering technology for energy production.