Biodiesel production by oleaginous bacteria Rhodococcus opacus PD630 using waste paper hydrolysate

Effective utilization of waste paper as a substrate for biodiesel production has environmental and economic advantages. To study the feasibility of using waste office automation paper to produce microbial lipids, waste paper hydrolysate (WPH) was prepared by enzymatic hydrolysis. WPH was fed to Rhodococcus opacus PD630 for microbial lipid production. Among the nitrogen sources tested, the medium with NH₄Cl yielded significantly high biomass and lipid of 4.92 and 1.29 g/L, respectively. When the ratio of C/N increases from 10 to 80, the lipid accumulation increases and the lipid content also increases from 18.92 to 43.41%. Under optimized conditions, the maximum biomass, lipid yield, and lipid content obtained were 6.51 g/L, 2.8 g/L, and 43% respectively. The extracted lipids exhibited similarities to those of vegetable oils. The carbon chain length of accumulated fatty acids ranged from C10 to C21, mainly oleic acid (31%). Moreover, biodiesel properties based on lipid profile yielded cetane number (59.88), iodine value (42.29 mg I₂/g), high heating value (44.26 MJ/kg), and density (0.9 g/cm³) were in the permissible limits of international standards. The present study gives a sustainable biorefinery approach for the production of biodiesel from waste office paper hydrolysate.