Production of microbial lipids from optimized waste office paper hydrolysate, lipid profiling and prediction of biodiesel properties

Waste office paper (WOP), was used to produce microbial lipids using Cryptococcus curvatus. Pretreatment of WOP with 1% (v/v) sulfuric acid removed the lignin without any inhibitor formation and increased the cellulose content. The optimum conditions for enzymatic hydrolysis of WOP were predicted at 92 h, 50 FPU/g cellulase, 50 CBU/g β-glucosidase, 5% substrate loading, 50 mL working volume and 156 rpm using the central composite design. The maximum sugar yield obtained in the validation experiment was 35.3 g/L. Ammonium chloride and yeast extract combination were more suitable for lipid production by C. curvatus with the carbon to nitrogen ratio of 60. A maximum biomass 11.48 ± 0.09 g/L was obtained at 120 h with a lipid yield of 4.95 ± 0.02 g/L. The lipid profile studies reveal the presence of 11 fatty acid methyl esters. These predominantly comprised of (%, w/w) 50.8% oleic acid, 25.7% palmitoleic acid, 7.1% stearic acid, and 6.5% myristic acid. The characteristic features of the biodiesel, such as cetane number, cold performance, density and iodine value met the requirements of the international standard (EN14214). Thus, the WOP could be a potential renewable feedstock to produce microbial lipids which are essential for the future sustainable production of biodiesel.