Abstract:

The anaerobic fermentation of food waste to produce chiral lactic acid achieves the high-value resource utilization of food waste, which is also an important component of the circular economy. However, food waste fermentation is limited by unstable pH and nutrient deficiencies. Landfill leachate contains a large amount of ammonia nitrogen, which can act as a buffering system to maintain a stable pH, and it also contains numerous trace elements that can effectively promote the growth of fermentative microflora. The study investigated the efficiency and mechanisms of lactic acid production through the co-fermentation of food waste and landfill leachate at different thermal pretreatment temperatures, which were utilized to lift the limitation of fermentation substrate solubilization and hydrolysis efficiency, and to change the microbial community composition and its functional activity. The results indicated that, compared to the 35℃ pretreatment group [(36.37±2.66)g COD/L, 55.85%], the production and the optical activity of L-lactic acid in the 45℃ group reached (40.16±0.75)g COD/L and 93.17%, which increased 10% and 67%, respectively. At higher temperatures (65℃ and 75℃), the relatively low L-lactic acid yield was associated with the higher activity of NAD-independent lactate dehydrogenase (lactic acid consumption). Additionally, increasing the thermal pretreatment temperature inhibited the production of D-lactic acid. Mechanistic studies indicated that thermal pretreatment could accelerate the solubilization and hydrolysis processes, speeding up the utilization and metabolism of carbohydrates. The total relative abundance of lactic acid bacteria such as Enterococcus, Klebsiella, Streptococcus, and Bavariicoccus reached 86.35% and 80.19% in the 45℃ and 55℃ thermal pretreatment groups, respectively. Functional analysis revealed that thermal pretreatment significantly enhanced carbohydrate metabolic pathways associated with lactic acid production. Compared to the 35℃ thermal pretreatment group (15.9%), the relative abundance of carbohydrate metabolic pathways increased to 16.87% and 17.74% in the 45℃ and 55℃ thermal pretreatment groups, respectively. This study provided a new approach to the recycling of food waste and landfill leachate.

Key words: thermal pre-treatment, food waste, landfill leachate, anaerobic, fermentation, lactic acid, metabolism

摘要：

餐厨垃圾厌氧发酵产生手性乳酸不仅实现了餐厨垃圾的高值资源化，同时是循环经济的重要组成。然而，餐厨垃圾厌氧发酵过程中存在pH不稳定和营养元素缺失等问题。垃圾渗滤液中包含大量氨氮可作为缓冲体系维持稳定的pH，同时存在大量微量元素可有效促进发酵菌群生长。本文以餐厨垃圾和垃圾渗滤液为底物，利用热预处理解除发酵底物溶出水解效率的限制，同时改变微生物群落组成及其功能活性，深入探讨了联合发酵产乳酸的效能及机制。结果表明，与35℃热预处理组相比[(36.37±2.66)g COD/L，55.85%，COD为化学需氧量]，45℃热预处理组中L-乳酸产量和光学活性可达(40.16±0.75)g COD/L和93.17%，分别提高了10%和67%。高温条件下（65℃和75℃）L-乳酸产量较低与较强的烟酰胺腺嘌呤二核苷酸(NAD)-非依赖型乳酸脱氢酶（i-LDH）活性相关（乳酸消耗）。此外，热预处理温度的增加会抑制D-乳酸生成。机理研究表明，热预处理能够加快底物溶出和水解进程，加速碳水化合物利用及其代谢进程，同时富集产乳酸微生物，肠球菌属（Enterococcus）、克雷伯菌属（Klebsiella）、链球菌属（Streptococcus）、巴伐利亚球菌属（Bavariicoccus）等产乳酸微生物45℃和55℃热预处理组总相对丰度分别达到86.35%和80.19%。功能分析发现，热预处理能够显著提高与乳酸生成相关的碳水化合物代谢通路丰度，与35℃热预处理组相比（15.9%），45℃和55℃热预处理组的碳水化合物代谢通路相对丰度提高到16.87%和17.74%。本文为餐厨垃圾与垃圾渗滤液资源化提供了新途径。

关键词: 热预处理, 餐厨垃圾, 垃圾渗滤液, 厌氧, 发酵, 乳酸, 代谢