窖泥来源产己酸精简菌群的生料发酵特性

Fermentation characteristics of unsterilized feedstock with a simplified caproate-producing microbial consortium

摘要:

【目的】 获得高效利用乳酸产己酸的稳定菌群，以实现对白酒酿造废水(黄水)的高值化碳回收处理。【方法】 采用平板筛选法获得产己酸精简菌群，评估菌群的底物利用类型，优化菌群的发酵底物浓度、最适pH值和补料策略，并运用基于纳米孔测序技术的宏基因组学分析产己酸精简菌群的结构和稳态特征。【结果】 产己酸精简菌群SimpCom1在乳酸条件下具有比葡萄糖条件更优的己酸转化能力；以生料黄水作为发酵原料时，黄水浓度控制在30%-50%、发酵起始pH 5.50的方式可实现菌群稳定生长与代谢；以50%黄水浓度、起始pH 5.50并在48 h后控制pH (6.50≤pH≤7.00)的批次补料发酵方式，四次批次发酵循环的平均己酸累积浓度为16.83 g/L，平均生产效率为3.05 g/(L·d)，平均己酸选择性(己酸占产生总酸比值)为67.27%，乳酸向己酸的平均转化得率为0.42 g/g；宏基因组学分析表明，SimpCom1菌群核心物种主要包括解乳酸己小杆菌(Caproicibacterium lactatifermentans)、酸鱼宿主关联乳杆菌(Ligilactobacillus acidipiscis)、酪丁酸梭菌(Clostridium tyrobutyricum)和‘Butyriproducens baijiuensis BJN0003’，其中解乳酸己小杆菌和‘B. baijiuensis BJN0003’可在生料黄水中有效生长与稳定代谢，在50%稀释度黄水发酵终点的相对丰度分别为45.3%和6.7%。【结论】 成功应用含解乳酸己小杆菌和‘B. baijiuensis BJN0003’的产己酸精简菌群发酵生料白酒酿造废水，实现高值、高效、低成本碳回收。

Abstract:

[Objective] To obtain a stable microbial consortium with a high yield of caproate and achieve high-value carbon recovery from Baijiu-making wastewater (Huangshui). [Methods] We used the plate screening approach to obtain a simplified caproate-producing microbial consortium, evaluated the preferred carbon source of the consortium, and optimized the substrate concentration, pH, and feeding strategy. The metagenomics based on nanopore sequencing was employed to determine the composition and stability characteristics of the simplified caproate-producing microbial consortium. [Results] SimpCom1, a simplified caproate-producing microbial consortium, demonstrated significantly higher conversion rate of lactate than glucose to caproate. When SimpCom1 was used to ferment unsterilized Huangshui, we controlled the working concentration of Huangshui between 30% and 50% and initial pH 5.50 to achieve stable growth and metabolism of the consortium for caproate production. The fermentation was carried out in a fed-batch manner with 50% Huangshui, initial pH 5.50, and pH 6.50-7.00 after 48 h. Within four fed-batch fermentation cycles, the average caproate titer, productivity, proportion of caproate in total acids, and conversion rate of lactate to caproate reached 16.83 g/L, 3.05 g/(L·d), 67.27%, and 0.42 g/g, respectively. The metagenomic analysis showed that Caproicibacterium lactatifermentans, Ligilactobacillus acidipiscis, Clostridium tyrobutyricum, and ‘Butyriproducens baijiuensis BJN0003’ were the core species of SimpCom1. C. lactatifermentans and ‘B. baijiuensis BJN0003’ remained stable growth and metabolism in the unsterilized Huangshui, with the relative abundance of 45.3% and 6.7%, respectively, at the end of fermentation with 50%-diluted Huangshui. [Conclusion] We successfully established an efficient and low-cost approach for producing caproate by fermentation of unsterilized Baijiu-making wastewater with a simplified microbial consortium containing C. lactatifermentans and ‘B. baijiuensis BJN0003’.