Abstract
Various challenges facing the industrial manufacture of biobased lactic acid (LA) have been occurred. These include substrate and/or pre-treatments cost, medium cost, and contamination risk as a result of utilizing neutral pH and mesophilic conditions. Therefore, this study focused on development of consolidated bioprocess for LA production from organic wastes under harsh conditions. A newly isolated thermo-alkali-tolerant lactic acid bacterium, Enterococcus durans BP130, was firstly used for direct LA production from banana peels (BP). Increasing the solid concentration of BP from 4.0% to 6.7% [w-(dry) (matter)/v] have resulted in increased fermentation efficiency with the highest LA production (19.2 g L-1) at 6.7% [w-(dry) (matter)/v]. Besides, co-fermentation of BP and food waste (FW) materials resulted in 13% improvements in LA concentration and 12% in LA productivity at 0.5:1 of FW:BP (w/w). Increasing of food waste concentrations could replace the nutritional components of the media and achieved increased LA production. Without any nutrients supplementation, food waste substituted the medium components and resulted in 14.3 g L-1 of LA produced using mixed substrates of FW:BP at 3:1 (w/w). The highest LA concentration of 28.8 g L-1 with a yield of 0.85 g g(-1)-consumed sugar and productivity of 0.24 g L-1 h(-1) was achieved in batch fermentation using CaCO3 as a neutralizing agent. This study introduced effective mixed waste-based biorefinery process for direct LA production in an inexpensive fermentation system.