Rahman Md Shafiqur, Xu Chunbao Charles, Ma Kesen, Nanda Malaya, Qin Wensheng
Department of Biology, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario, P7B 5E1, Canada;; Department of Microbiology, University of Chittagong, Bangladesh.
Institute for Chemicals and Fuels from Alternative Resources (ICFAR), Western University, London, Ontario N6A 5B9, Canada.
Int J Biol Sci. 2017 Feb 23;13(3):308-318. doi: 10.7150/ijbs.17594. eCollection 2017.
Biodiesel, a renewable fuel produced by transesterification of animal fats and vegetable oils, generates about 10% (v/v) of crude glycerol as a core byproduct. The high volume of this non bio-degradable glycerol is becoming of a great environmental and economical concern due to its worldwide ever-growing surplus. Herein we report a high production of 2,3-butanediol (2,3-BD) from pure and biodiesel derived crude glycerol using a mutant SRM2 obtained from a newly isolated strain SRP2. The mutant strain SRM2 with standing high glycerol concentration (220 g L of medium) could rapidly convert glycerol aerobically to 2,3-BD, a versatile product extensively used in chemical, pharmaceutical and fuel industries Our study revealed that an increased GDH activity led to a substantially enhanced production of 2,3-BD. The mutant strain exhibited 1.3-fold higher activity of GDH than that of parent strain (500.08 vs. 638.6 µmol min mg protein), yielding of 32.3 g L and 77.5 g L 2,3-BD with glycerol in batch and fed-batch process respectively. However, in batch culture with crude glycerol, cell growth and glycerol consumption were expressively boosted, and 2,3-BD production was 27.7 g L from 75.0 g/L crude glycerol. In this report, the optimal conditions for high production of 2,3-BD were defined in a completely aerobic process, and 0.59 g g product yield of 2,3-BD was attained by the mutated strain SRM2, which is the highest amount obtained from batch biotransformation process of glycerol metabolism till today. These results indicated that our newly developed mutant can tolerate high concentration of glycerol, have a high glycerol utilization rate, and high product yield of 2,3-BD. It is demonstrated that the mutant strain SRM2 has an ability to produce fewer co-products at trace concentrations at higher glycerol concentrations, and could be a potential candidate for 2,3-DB production in an industrial bioconversion process.
生物柴油是通过动物脂肪和植物油的酯交换反应生产的一种可再生燃料，其核心副产品粗甘油的产量约为10%（体积/体积）。由于全球范围内这种不可生物降解的甘油过剩量不断增加，其大量存在正引起极大的环境和经济关注。在此，我们报告了使用从新分离菌株SRP2获得的突变体SRM2，从纯甘油和生物柴油衍生的粗甘油中高产2,3-丁二醇（2,3-BD）。突变菌株SRM2能够耐受高甘油浓度（培养基中220 g/L），可在有氧条件下迅速将甘油转化为2,3-丁二醇，这是一种广泛应用于化工、制药和燃料行业的多功能产品。我们的研究表明，GDH活性的提高导致2,3-丁二醇产量大幅增加。突变菌株的GDH活性比亲本菌株高1.3倍（分别为500.08和638.6 μmol min mg蛋白质），在分批培养和补料分批培养过程中，以甘油为原料分别产生32.3 g/L和77.5 g/L的2,3-丁二醇。然而，在使用粗甘油的分批培养中，细胞生长和甘油消耗显著增加，从75.0 g/L粗甘油中产生的2,3-丁二醇产量为27.7 g/L。在本报告中，确定了在完全有氧过程中高产2,3-丁二醇的最佳条件，突变菌株SRM2实现了2,3-丁二醇0.59 g/g的产物产率，这是迄今为止甘油代谢分批生物转化过程中获得的最高产量。这些结果表明，我们新开发的突变体能够耐受高浓度甘油，甘油利用率高，2,3-丁二醇产物产率高。结果表明，突变菌株SRM2在较高甘油浓度下产生微量副产物的能力较低，可能是工业生物转化过程中生产2,3-丁二醇的潜在候选菌株。
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