Department of Food Science and Technology, Virginia Tech, Blacksburg, Virginia, USA.
Department of Mining and Minerals Engineering, Virginia Tech, Blacksburg, Virginia, USA.
J Food Sci. 2022 Jul;87(7):3071-3083. doi: 10.1111/1750-3841.16205. Epub 2022 Jun 6.
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. PRACTICAL APPLICATION: Food waste is one of the largest municipal solid wastes in the US, and most food waste ends up in landfills, causing significant economic losses and environmental concerns. In this study, we developed a fermentation process to convert food waste into biorenewable lactic acid and demonstrated that food waste is a superior feedstock for fermentation due to its embedded nutrients. Moreover, due to the embedded nutrients in food waste, the supplementation of yeast extract and peptone to fermentation can be reduced by over 50%, which can reduce the operating cost of lactic acid fermentation on an industrial scale.
利用发酵从食物垃圾中生产乳酸具有环境可持续性。然而，由于食物垃圾的复杂性，食物垃圾发酵生产乳酸的特性尚不清楚。本研究旨在了解关键变量对食物垃圾发酵特性的影响，以最大限度地提高乳酸产量。采用戊糖乳杆菌对食物垃圾进行酶解发酵。在分批发酵中研究了氮营养物补加、初始糖浓度和 pH 等关键发酵变量，以揭示它们对发酵产率、产率和生产力的影响。结果表明，向食物垃圾发酵培养基中补加 0.25%（w/v%）酵母提取物和蛋白胨可显著提高发酵产率和生产力，但进一步增加补加水平并不能改善发酵。将初始糖浓度从 40 g/L 增加到 100 g/L，可将发酵产率从 41.0 g/L 提高到 93.0 g/L，产率从 0.34 g/L/h 提高到 0.76 g/L/h。pH 6.0 是发酵的最佳 pH 值。在最佳条件下，食物垃圾发酵的最高发酵产率、产率和生产力分别为 106.7 g/L、1.12 g/g 和 3.09 g/L/h。1.12 g/g 的高发酵产率可能是由于食物垃圾水解物中未知化合物产生了额外的乳酸。通过应用补料分批发酵，乳酸浓度达到 157.0 g/L，产率和整体生产力分别为 0.92 g/g 和 2.0 g/L/h。根据质量平衡，从 1000 公斤食物垃圾中总共生产了 251 公斤乳酸。实际应用：食物垃圾是美国最大的城市固体废物之一，大部分食物垃圾最终都被填埋，造成了巨大的经济损失和环境问题。在这项研究中，我们开发了一种发酵工艺，将食物垃圾转化为生物可再生乳酸，并证明由于食物垃圾中嵌入的营养物质，它是发酵的优良原料。此外，由于食物垃圾中嵌入的营养物质，发酵过程中酵母提取物和蛋白胨的补加量可以减少 50%以上，这可以降低乳酸发酵在工业规模上的运营成本。
