Enabling cassava starch hydrolysate for Pseudozyma tsukubaensis YWT 7-2 oil production using Ca(OH)2 treatment

Abstract

Cassava starch hydrolysate (CSH) was evaluated as feedstock for Pseudozyma tsukubaensis YWT 7-2 oil production using a two-step cultivation method. P. tsukubaensis YWT 7-2 produced oil in the CSH (without supplementation) only after the CSH was treated with Ca(OH)2 at pH 10 (CaCSH). Addition of 0.1% (weight per volume, w/v) KH2PO4 into the CaCSH containing 0.2% (w/v) (NH4)2SO4 increased the resultant cell mass 1.49-fold in the cell propagation step, while supplementation of the CaCSH with 0.25% (w/v) (NH4)2SO4 increased the oil titer 2.52-fold in the oil production step. The optimal pH and cell inoculum for oil production were 5.5 and 8.05 g (dry cell weight)/L, respectively. The major fatty acids in the oil from P. tsukubaensis YWT 7-2 grown in CaCSH were palmitic (47.8%) and oleic (36.96%) acids, somewhat similar to those of palm oil and so indicating their potential use as feedstock for biodiesel production. The results showed that the Ca(OH)2 treatment of CSH, which is high in sugar but low in nitrogen, was indispensable for P. tsukubaensis YWT 7-2 oil production.