Deng Yu, Mao Yin, Zhang Xiaojuan
National Engineering Laboratory for Cereal Fermentation Technology (NELCF), Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; The Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China.
National Engineering Laboratory for Cereal Fermentation Technology (NELCF), Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; The Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China.
J Biotechnol. 2015 Dec 20;216:151-7. doi: 10.1016/j.jbiotec.2015.10.022. Epub 2015 Nov 1.
Butyric acid, a 4-carbon short chain fatty acid, is widely used in chemical, food, and pharmaceutical industries. The low activity of butyryl-CoA: acetate CoA-transferase in Thermobifida fusca muS, a thermophilic actinobacterium whose optimal temperature was 55°C, was found to hinder the accumulation of high yield of butyric acid. In order to solve this problem, an exogenous butyryl-CoA: acetate CoA-transferase gene (actA) from Thermoanaerobacterium thermosaccharolyticum DSM571 was integrated into the chromosome of T. fusca muS by replacing celR gene, forming T. fusca muS-1. We demonstrated that on 5g/L cellulose, the yield of butyric acid by the engineered muS-1 strain was increased by 42.9 % compared to the muS strain. On 100g/L of cellulose, the muS-1 strain could consume 90.5% of total cellulose in 144h, with 33.2g/L butyric acid produced. Furthermore, on the mix substrates including the major components of biomass: cellulose, xylose, mannose and galactose, 70.4g/L butyric acid was produced in 168h by fed-batch fermentation. To validate the ability of fermenting biomass, the muS-1 strain was grown on the milled corn stover ranging from 200 to 250μm. The muS-1 strain had the highest butyrate titer 17.1g/L on 90g/L corn stover.
丁酸是一种4碳短链脂肪酸，广泛应用于化工、食品和制药行业。在嗜热放线菌嗜热栖热放线菌muS中，其最适温度为55°C，发现丁酰辅酶A：乙酸辅酶A转移酶的低活性阻碍了高产丁酸的积累。为了解决这个问题，通过替换celR基因，将来自嗜热解糖嗜热厌氧菌DSM571的外源丁酰辅酶A：乙酸辅酶A转移酶基因（actA）整合到嗜热栖热放线菌muS的染色体中，形成嗜热栖热放线菌muS-1。我们证明，在5g/L纤维素上，工程化的muS-1菌株的丁酸产量比muS菌株提高了42.9%。在100g/L的纤维素上，muS-1菌株在144小时内可以消耗90.5%的总纤维素，产生33.2g/L的丁酸。此外，在包括生物质主要成分纤维素、木糖、甘露糖和半乳糖的混合底物上，通过分批补料发酵在168小时内产生了70.4g/L的丁酸。为了验证发酵生物质的能力，将muS-1菌株接种在粒径为200至250μm的磨碎玉米秸秆上。muS-1菌株在90g/L玉米秸秆上的丁酸产量最高，为17.1g/L。
