Environmental Technology, Wageningen University & Research, Bornse Weilanden 9, 6708, WG, Wageningen, the Netherlands.
Institute of Biology, Leiden University, Sylviusweg 72, 2333, BE, Leiden, the Netherlands; Department of Microbial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, the Netherlands.
Water Res. 2020 Feb 1;169:115215. doi: 10.1016/j.watres.2019.115215. Epub 2019 Oct 23.
The production of biochemicals from renewables through biorefinery processes is important to reduce the anthropogenic impact on the environment. Chain elongation processes based on microbiomes have been successfully developed to produce medium-chain fatty acids (MCFA) from organic waste streams. Yet, the sustainability of chain elongation can still be improved by reducing the use of electron donors and additional chemicals. This work aimed to couple lactate production and subsequent chain elongation to decrease chemicals input such as electron donors and hydroxide for pH control in repeated-batch food waste fermentation. Food waste with adjusted pH was used as substrate and fermentation proceeded without pH control. During fermentation, lactate was first formed through the homolactic pathway and then converted to fatty acids (FA), mainly n-butyrate and n-caproate. The highest n-caproate carbon selectivities (mmol C/mmol C) and production rates were 38% and 4.2 g COD/L-d, respectively. Hydroxide input was reduced over time to a minimum of 0.47 mol OH/mol MCFA or 0.79 mol OH/kg COD. Lactate was a key electron donor for chain elongation and its conversion was observed at pH as low as 4.3. The microbiome enriched in this work was dominated by Lactobacillus spp. and Caproiciproducens spp. The high abundance of Caproiciproducens spp. and their co-occurrence with Lactobacillus spp. suggest Caproiciproducens spp. used lactate as electron donor for chain elongation. This work shows the production of n-caproate from food waste with decreased use of hydroxide and no use of exogenous electron donors.
通过生物炼制过程从可再生资源生产生物化学物质对于减少人为对环境的影响非常重要。基于微生物组的链延长过程已经成功开发，用于从有机废物流中生产中链脂肪酸 (MCFA)。然而，通过减少电子供体和其他化学物质的使用，链延长的可持续性仍然可以提高。本工作旨在耦合乳酸生产和随后的链延长，以减少化学物质的投入，例如电子供体和氢氧化物，用于重复批次的食品废物发酵中的 pH 控制。调节 pH 的食品废物用作底物，发酵过程中不进行 pH 控制。在发酵过程中，乳酸首先通过同型乳酸途径形成，然后转化为脂肪酸 (FA)，主要是正丁酸和正己酸。最高的正己酸碳选择性 (mmol C/mmol C) 和产率分别为 38%和 4.2 g COD/L-d。随着时间的推移，氢氧化物的输入逐渐减少到最低 0.47 mol OH/mol MCFA 或 0.79 mol OH/kg COD。乳酸是链延长的关键电子供体，在 pH 低至 4.3 时就观察到其转化。本工作中富集的微生物组主要由 Lactobacillus spp. 和 Caproiciproducens spp. 组成。Caproiciproducens spp. 的高丰度及其与 Lactobacillus spp. 的共现表明 Caproiciproducens spp. 将乳酸用作链延长的电子供体。这项工作表明可以从食品废物中生产正己酸，同时减少氢氧化物的使用，并且不使用外源电子供体。
