Enzymatic biodiesel synthesis from Trichosporon shinodae yeast through circular economy: A greener approach

Abstract

In the present study, crude glycerol, a by-product of biodiesel production, was supplemented to Trichosporon shinodae for higher lipid synthesis and further extracted (lipid) using ultrasonic-assisted extraction (UAE). Optimization of enzymatic transesterification (ET) using Response Surface Methodology (RSM) coupled with Central Composite Design (CCD) quadratic model of single-cell oil resulted in 90.03%(v/v) of maximum FAME's yield with methanol to oil ratio of 14.98, solvent to oil ratio of 0.270 in 12.52 h at 25.99 °C with 1.26%(v/v) initial water content. The developed model was significant, with an R2 value of 95.20% and an adj.R2 value of 91.97%. The developed RSM model was further utilized for optimization through the Modified Chaotic Invasive Weed Optimization (MC-IWO). The optimization results showed a maximum FAME's yield of 90.03% utilizing the MC-IWO parameters of 5 seeds with a 6% initial standard deviation using an exponent value of 2 with a population size of 15 in 56 generations. FAME's characterization of T. shinodae has revealed 58.8% (v/v) of saturated FAME's and 41.2% (v/v) of FAME's predominantly with oleic acid methyl ester content (38%,v/v). Fuel properties of T. shinodae showed kinematic viscosity of 3.9–4.4 mm2/s, iodine value (113–115 g I2/100 g), cetane index (46–48), saponification value (203–206 mg/KOH), acid value (1.2–1.4 mg KOH/g) and higher heating value (39–40 MJ/kg). Blending experiments of T. shinodae biodiesel with conventional petroleum showed calorific values of B5, B20 and B100 were 48.63 MJ/kg, 43.45 MJ/kg and 38.35 MJ/kg, respectively. This study showed the potential of T. shinodae biodiesel, which can be used either as an additive or as a blend of conventional fuels.