Lactic Acid Production from Cassava Processing Wastewater Fermentation by Autochthonous Mixed Microbial Culture: Effects of pH and Temperature

Abstract Cassava processing wastewater (CPWW) is an inexpensive feedstock that can be used to produce lactic acid (LA) through biotechnological processes. While previous studies have focused on pure culture fermentation, we propose a cheaper solution in which the autochthonous microbial community of the CPWW is used instead. A 3 2 full factorial design was used to investigate the effects of temperature (25 °C; 30 °C; and 35 °C) and initial fermentation pH (4.5; 5.5; and 6.5) on LA production. The results showed that temperature positively impacted lactic fermentation. LA selectivity was increased under acidic conditions, but initial pH did not affect LA yield and volumetric productivity. Interactions effects were statistically significant, implying that the increase in initial pH reduces the production of LA at higher temperatures, while the opposite occurs at lower temperatures. The best performing condition was 35 °C and pH 4.5, which resulted in a LA selectivity of 0.9 g COD-LA g COD −1 . Microbial community analysis revealed that the autochthonous consortium in CPWW was composed mostly of Lactobacillus . The results show that temperature and initial pH can steer the indigenous microbial community from the CPWW towards better LA production. Graphical Abstract