Lactic acid production from food waste hydrolysate by Lactobacillus pentosus: Focus on nitrogen supplementation, initial sugar concentration, pH, and fed‐batch fermentation

Abstract

Lactic acid production from food waste via fermentation is environmentally sustainable. However, the characteristics of food waste fermentation to produce lactic acid are not well understood due to the complexity of food waste. This study aims to understand the effects of key variables on the characteristics of food waste fermentation to maximize lactic acid production. Food waste was enzymatically hydrolyzed and fermented by Lactobacillus pentosus.Key fermentation variables, including nitrogenous nutrient supplementation, initial sugar concentration, and pH, were investigated in batch fermentation to unveil their effects on fermentation titer, yield, and productivity. The results showed that supplementation of 0.25% (w/v%) yeast extract and peptone to the food waste fermentation media significantly improved fermentation titer and productivity, but further increase in the supplementation level did not improve fermentation. Increasing the initial sugar concentration from 40 g/L to 100 g/L increased the fermentation titer from 41.0 g/L to 93.0 g/L and productivity from 0.34 g/L/h to 0.76 g/L/h. pH 6.0 was the optimal pH for the fermentation. At the optimal conditions, food waste fermentation resulted in the highest fermentation titer, yield, and productivity of 106.7 g/L, 1.12 g/g, and 3.09 g/L/h, respectively.The high fermentation yield of 1.12 g/g might be explained by the extra lactic acid production from unidentified compounds in food waste hydrolysates. By applying fed-batch fermentation, the lactic acid concentration reached 157.0 g/L with a yield and overall productivity of 0.92 g/g and 2.0 g/L/h, respectively. Based on the mass balance, a total of 251 kg lactic acid was produced from 1000 kg food waste.

Deep Shotgun metagenomic and 16S rRNA analysis revealed the microbial diversity of lactic acid bacteria in traditional fermented foods of eastern Hainan, China

“…Lactobacillus growth itself produces large amounts of lactic acid, and reduces the pH of the environment, creating an acidic environment that inhibits the growth of other bacteria. 54 Some traditional fermented foods will add salt during the production process to form a better flavor and inhibit the growth of miscellaneous bacteria. In addition, lactic acid bacteria in the process of fermentation can produce a variety of antibacterial substances, including organic acids, hydrogen peroxide, carbon dioxide, diacetyl and bactericins, which can inhibit the growth of harmful bacteria.…”

Advanced Fermentation Techniques for Lactic Acid Production from Agricultural Waste

“…Fed-batch fermentation of L. casei led to a 69.24% increase in LA production and 11% increase in yield [63]. In LA production from food waste by L. pentous, fed-batch mode further increased LA concentration from 106.7 g/L to 157.0 g/L, although the overall productivity decreased from 3.09 g/(L•h) to 2.0 g/(L•h) [64]. Feeding strategies might have positive effects on the metabolism of the microorganism.…”

Lactic Acid Fermentation of Carrageenan Hydrolysates from the Macroalga Kappaphycus alvarezii: Evaluating Different Bioreactor Operation Modes

“…Maintaining galactose concentrations at a fixed level of about 5 g/L (Figure 4) was achieved with an addition of less than 1 g/h of galactose to fermentation media while operating at a continuous feeding rate, leading to an extended fermentation of more than four days. Fermenting hydrolyzed food waste with L. pentosus, Lobeda et al [35] used three additional pulse injections of 100 mL of 400 g/L glucose and fructose concentrated food waste hydrolysates, reaching 157 g/L of lactic acid in about 80 h of fermentation. After the third injection, an amount of 125 g/L of lactic acid remained in the bioreactor, but the microorganism was unable to further consume substrate and continue the production of lactic acid.…”

“…Comparing a fed-batch after 24 h in fermentation systems with simple batch fermentation of lactic acid by L. plantartum (of which L. pentosus is a sub-species), Machado et al [34] found that lactate concentration was about 20 g/L higher when feeding glucose and xylose to the medium after all glucose was depleted. Investigating the potential of lactic acid production of L. pentosus, Lobeda et al [35] reached a high 157 g/L of lactic acid solution using three pulses of a 400 g/L solution of glucose and fructose.…”