Maximized Utilization of Raw Rice Bran in Microbial Oils Production and Recovery of Active Compounds: A proof of concept

Abstract

Lignocellulosic biomass is currently considered as one of the promising feedstock for petroleum diesel alternative, together with single cell oils. Rice bran, which is a very abundant waste especially in Asia, could be utilized better than just as cattle feed. Dilute acid hydrolysis using 3 % H2SO4 at 90 °C was found to be able to maximize the sugar produced from raw rice bran without prior oil extraction (TRS = 54.91 g/L). Activated carbon was used for removing most furan inhibitors from rice bran hydrolysate (RBH) after hydrolysis and resulted in a TRS of 50.10 g/L. RBH was then neutralized using calcium hydroxide and diluted to a TRS concentration of 30 g/L. RBH was used to culture Yarrowia lipolytica PO1g, resulting in a comparable results of lipid content to that cultured in complex medium (YPD). The highest crude lipid content obtained from Y. lipolytica cultivated in RBH with addition of 10 g/L yeast extract was 23.94 % (biomass = 14.3 g/L), while the optimum result obtained using YPD was at a C/N ratio of 9.5 (biomass reached 14.7 g/L) and crude lipid content was 28.42 %. Furthermore, lipid and γ-oryzanol can be recovered after dilute acid hydrolysis.