L(+)-LACTIC ACID PRODUCTION USING SUGARCANE MOLASSES AND WASTE POTATO STARCH: AN ALTERNATIVE APPROACH

L(+)-LACTIC ACID is a commonly occurring organic acid. It is widely used in the food and food-related industries, and has the potential to be used for the production of biodegradable polymers, solvents and oxygenated chemicals. Lactic acid can be produced by both bacteria and fungi, however it is currently produced from sugar-containing materials by bacteria such as Lactobacillus and Lactococcus. The main disadvantage of using bacteria is that expensive nutrients such as yeast extract and peptone are required. Unlike the lactic acid-producing bacteria, fungi strains (such as Rhizopus arrhizus) can grow under nutrientlimited conditions. This study examines the production of lactic acid from sugarcane molasses and waste potato starch by the fungus Rhizopus arrhizus. A high lactic acid concentration of 103.8 g/L could be achieved in 48 h fermentation using waste potato starch as substrate with the addition of 0.25 g/L KH2PO4, 0.15 g/L MgSO4·7H2O, 0.04 g/L ZnSO4·7H2O and 3.0 g/L (NH4)2SO4. Although the lactic acid concentration was lower (less than 60 g/L) using sugarcane molasses as substrate, it may be improved further by using appropriate cultivation strategies.