Exploiting Self‐Immobilized Fungi for Biovalorization of Oil Palm Sap to Organic Acids Through Repeated‐Batch Fermentation.

This study focused on utilizing agricultural waste, oil palm sap (OPS) as a sole nutrient source for organic acid production by self‐immobilized fungi. Among the fungi cultured in OPS, Rhizopus oryzae TISTR 3336 was selected as it could form compact and adequate‐size pellets (3–5 mm) and gave the highest total acid production yield of 0.31 ± 0.02 g/g‐sugar under pH control. The optimal conditions were as follows: inoculum size of 106 spores/mL and shaking speed of 120 rpm. Using concentrated OPS gave higher final concentration of organic acids but reduced the production yield. The repeated‐batch fermentation of OPS by self‐immobilized fungi was successfully carried out for four cycles. The optimal initial sugar concentration was 40 g/L, giving the organic acid productions ranging of 19 to 35 g/L, with yields ranging of 0.47 to 0.87 g/g‐sugar. This study has shown the efficient bioconversion of agricultural wastes into organic acids using self‐immobilized fungi in the repeated‐batch fermentation. [ABSTRACT FROM AUTHOR]