The effects of various pH and temperature to enhance lactic acid production using Lactobacillus casei and Lactobacillus rhamnosus

Abstract

Arenga pinnata waste (APW) is one of the side products of the agricultural industry and abundant availability and has not used optimally. This research aims to investigate the effects of pH and temperature to enhance lactic acid production. APW contains 25.63 % of cellulose, 12.98 % of hemicellulose and 29.35 % of lignin. The presence of lignin in APW can inhibit lactic acid production. Therefore it must be eliminated with the pretreatment process. The pretreatment process consisted of acid-organosolv pretreatment to reduce lignin. Subsequently, enzymatic hydrolysis process with cellulase enzyme from Trichoderma reesei to produce reducing sugar for a lactic acid substrate. The acid-organosolv pretreatment using 0.2 M H2SO4 at 120°C for 40 minutes and ethanol 30 %(v/v) with NaOH 3%(v/v) as a catalyst at 107°C for 33 minutes can increase the cellulose content to 56.33 % and decreased lignin content to 27.09 %. Meanwhile, the lactic acid fermentation process with various pH (4.5; 6.5; 7.5) and Temperature (29°C; 33°C; 37°C; 41°C) using Lactobacillus casei and Lactobacillus rhamnosus. The highest lactic acid concentration obtained after 48 h of incubation at 37°C with pH 6.5 is 4.261 g/L for Lactobacillus casei and 3.523 g/L for Lactobacillus rhamnosus.