A newly isolated strain, Lactobacillus paracasei subsp. paracasei 2, produces l‐lactic acid from pilot‐scale fermentation of food waste under sterile and nonsterile conditions

Abstract

AbstractBACKGROUNDLactic acid (LA) is a valuable industrial chemical with wide applications. Presently, the demand for optically pure l‐LA has grown considerably as a result of its applications in the food and pharmaceutical industries, and biodegradable polylactic acid production. The production of l‐LA from food waste (FW) has been discussed in some studies; however, most fermentation is performed under sterile conditions and with the addition of specific lactic acid bacteria. Completely autoclaving organic solid wastes is difficult and economically unfeasible. The aim of this work was to investigate pilot‐scale LA production from FW under sterile and nonsterile conditions.RESULTSWhen FW was fermented without sterilization and inoculation, the maximum yield of LA was 0.43 g LA g–1 total solid (TS) and the proportion of l‐LA was only ≈50%. A newly isolated strain, Lactobacillus paracasei subsp. paracasei 2, which was isolated and identified from FW, was used to improve the proportion of l‐LA in total LA. When nonsterile FW was inoculated with this strain, the proportion of l‐LA increased to 72.3%. After FW was sterilized and inoculated with this strain, the proportion of l‐LA was 98.6% and 98.8% under intermittent and real‐time regulation of pH level, respectively. The maximum LA yield could increase to 0.55 g LA g–1TS.CONCLUSIONPilot‐scale LA production from FW was determined by comparing the isomer purity of l‐LA between sterilization and nonsterilization and between inoculation and noninoculation, which provided an important strain and fermentation type for production of high concentration of l‐LA. © 2020 Society of Chemical Industry