Production of lactic acid from date fruit pomace using Lactobacillus casei and the enzyme Cellic CTec2

Abstract

A circular, sustainable bioeconomy is gaining ground across the globe. Green synthesis, which uses renewable feedstock, is becoming a mainstay of the chemical industry. To produce polylactic acid, a biodegradable plastic, researchers are increasingly focusing on low-cost substrates to produce lactic acid. In the United Arab Emirates, one such low-cost substrate with readily available reducing sugar is the date fruit pomace (DFP). It is a solid residue obtained from date fruit processing and contains 35% sugars on a dry basis. It is a potential feedstock for lactic acid fermentation. Here, the effects of media supplements and fermentation parameters on L-lactic acid production by Lactobacillus casei were investigated. The lactic acid yield improved when the pH was maintained at 6.2 during incubation and the enzyme Cellic CTec2 was used to release sugar from the pomace. At a controlled pH, a lactic acid concentration of 292 ± 1.2 g/kg DFP was achieved when 80 g DFP was inoculated with bacteria (3.9 × 1010 colony-forming units) and incubated for 7 days. Upon hydrolysis with 40 FPU/g DFP Cellic CTec2, the sugar content increased to 482 g/kg DFP, and the lactic acid concentration increased to 457 ± 1.4 g/kg DFP. Using n-butanol, via phase partitioning, 78.9% pure L-lactic acid was extracted from the fermentation broth.

Keywords: Date fruit pomace, L-lactic acid, Lactobacillus casei, Controlled Ph, Cellic CTec2 enzyme