Lactic acid production with two types of feedstocks from food waste: Effect of inoculum, temperature, micro-oxygen, and initial pH.

[Display omitted] • Fruit and vegetable waste has greater potential for LA production than kitchen waste. • Using LAB as inoculum improved the maximum LA concentration by 50.8%. • Optimal temperature of LA production was 37 °C for Fruit and vegetable waste and 50 °C for Kitchen waste. • Micro-oxygen limited Acetobacter growth then decreased VFAs formation. Lactic acid (LA) is an important chemical with broad market applications. To optimize LA production, food waste has been explored as feedstock. Due to the wide variety of food waste types, most current research studies have obtained different conclusions. This study focuses on carbohydrate-rich fruit and vegetable waste (FVW) and lipid-rich kitchen waste (KW), and the effect of inoculum, temperature, micro-oxygen, and initial pH were compared. FVW has a greater potential for LA production than KW. As an inoculum, lactic acid bacteria (LAB) significantly increased the maximum LA concentration (27.6 g/L) by 50.8 % compared with anaerobic sludge (AS). FVW exhibited optimal LA production at 37 °C with micro-oxygen. Adjustment of initial pH from 4 to 8 alleviated the inhibitory effect of accumulated LA, resulting in a 46.2 % increase in maximum LA production in FVW. The expression of functional genes associated with metabolism, genetic information processing, and environmental information processing was higher at 37 °C compared to 50 °C. [ABSTRACT FROM AUTHOR]