Bioconversion of Agro-Residues into Microbial Oil-Based Oleochemicals Employing Packed Bed Bioreactor
Lignocellulosic waste-streams are resources worth investigating to produce value-added bioproducts due to their low-cost, renewability, versatility, and abundance. This study evaluated five Zygomycota strains as potential oleaginous microorganisms for direct bioconversion of cakes derived from the vegetable-oil-milling industry into microbial oil. Solid-state fermentation (SSF) conditions in tray bioreactors revealed that temperature, moisture content, and substrate affected lipid production and fatty acids composition. Employing SSF, under optimal conditions (30 &deg;C, 65% initial moisture content), and substrate supplementation with nitrogen sources increased lipid productivity 1.1-fold on palm kernel cake (PKC) substrate. Supplementation strategies using glycerol, molasses, or mineral solution did n&omicron;t favor lipid production. When cotton seed cake (CoSC) was applied, C. echinulata was able to produce 304.1 mg/gfs of biomass with a lipid content of 40.2% (w/w) in tray bioreactors. Scaling-up SSF using CoSC in packed bed reactors led to the highest biomass production (320.5 mg/gfs), while lipids production was unaffected. Then, microbial oil was enzymatically converted into polyol esters achieving the highest conversion yield of 80% after 2 h. Physicochemical properties of polyol esters demonstrated their potential utilization as biolubricants. The present study showed the perspective of bioconverting industrial side streams into microbial oil and a route for sustainable synthesis of oleochemicals.