Guo W, Li D, He R, Wu M, Chen W, Gao F, Zhang Z, Yao Y, Yu L, Chen S
Tianjin Key Laboratory for Industrial Biological Systems and Bioprocessing Engineering, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Science, Tianjin, China.
Food and Environmental Department, Dalian University of Technology, Panjin, China.
J Appl Microbiol. 2017 Nov;123(5):1214-1227. doi: 10.1111/jam.13581.
Methane and methanol are potential carbon sources of industrial micro-organisms in addition to crop-derived bio-carbon sources. Methanotrophs that can utilize these simple, stable and large amounts chemicals are expected to be developed into 'cell factories' for the production of specific chemicals. In this study, a methanotroph that can synthesize lycopene, C carotenoid and exopolysaccharides (EPS) with relative better performances from C1 substrates was isolated, and its performances were evaluated.
The isolated strain was identified as Methylomonas sp. ZR1 based on 16S rRNA sequence analysis. Its maximum specific growth rate achieved 0·200 h under flask culture conditions, and 0·386 h in bubble column reactors. ZR1 was able to utilize 35 g l of methanol and even exhibited slight growth in the presence of 40 g l of methanol. Furthermore, ZR1 was proved to synthesize lycopene (C carotenoids) besides the C carotenoids through HPLC-DAD and HPLC-MS/MS analysis methods. Its carotenoid extracts exhibited excellent antioxidative activities measured by the ABTS method. Plenty of polysaccharides were also synthesized by ZR1, the components of the polysaccharides were identified as glucose, mannose and galactose with a proportion of 1 : 2 : 1 by GC-MS, and its yield achieved 0·13 g g cell dry weight.
The isolated strain has great potential for the production of value-added bioproducts from C1 compounds because of its excellent C1 substrate utilizing abilities and its abilities to naturally synthesize lycopene, C carotenoids and EPS.
In this study, we isolated a fast-growing methanotroph, its C1 carbon substrate utilizing ability is excellent in comparison with reported methanotrophs. Furthermore, besides polysaccharides and C carotenoids which were commonly synthesized by methanotrophs, our findings suggested that C lycopene could also be naturally synthesized from methane by methanotrophs.
除了源自农作物的生物碳源外，甲烷和甲醇是工业微生物潜在的碳源。有望开发出能够利用这些简单、稳定且大量的化学物质的甲烷氧化菌，使其成为用于生产特定化学品的“细胞工厂”。在本研究中，分离出了一种能从C1底物合成番茄红素、C类胡萝卜素和胞外多糖（EPS）且性能相对较好的甲烷氧化菌，并对其性能进行了评估。
基于16S rRNA序列分析，将分离出的菌株鉴定为甲基单胞菌属ZR1。在摇瓶培养条件下，其最大比生长速率达到0.200 h⁻¹，在鼓泡塔反应器中为0.386 h⁻¹。ZR1能够利用35 g/L的甲醇，甚至在40 g/L甲醇存在的情况下仍有轻微生长。此外，通过高效液相色谱 - 二极管阵列检测法（HPLC - DAD）和高效液相色谱 - 串联质谱法（HPLC - MS/MS）分析方法证明，ZR1除了合成C类胡萝卜素外，还能合成番茄红素。通过ABTS法测定，其类胡萝卜素提取物表现出优异的抗氧化活性。ZR1还合成了大量多糖，通过气相色谱 - 质谱联用（GC - MS）鉴定多糖的成分是葡萄糖、甘露糖和半乳糖，比例为1∶2∶1，其产量达到0.13 g/g细胞干重。
由于其优异的C1底物利用能力以及天然合成番茄红素、C类胡萝卜素和EPS的能力，分离出的菌株在利用C1化合物生产高附加值生物产品方面具有巨大潜力。
在本研究中，我们分离出了一种生长迅速的甲烷氧化菌，与已报道的甲烷氧化菌相比，其C1碳底物利用能力优异。此外，除了甲烷氧化菌通常合成的多糖和C类胡萝卜素外,我们的研究结果表明甲烷氧化菌还能从甲烷中天然合成C番茄红素。
