Cassman Noriko A, Lourenço Késia S, do Carmo Janaína B, Cantarella Heitor, Kuramae Eiko E
1Department of Microbial Ecology, Netherlands Institute of Ecology NIOO-KNAW, Wageningen, Netherlands.
Soils and Environmental Resources Center, Agronomic Institute of Campinas, P.O. Box 28, Campinas, SP 13012-970 Brazil.
Biotechnol Biofuels. 2018 Feb 22;11:48. doi: 10.1186/s13068-018-1036-9. eCollection 2018.
The production of 1 L of ethanol from sugarcane generates up to 12 L of vinasse, which is a liquid waste containing an as-yet uncharacterized microbial assemblage. Most vinasse is destined for use as a fertilizer on the sugarcane fields because of the high organic and K content; however, increased NO emissions have been observed when vinasse is co-applied with inorganic N fertilizers. Here we aimed to characterize the microbial assemblage of vinasse to determine the gene potential of vinasse microbes for contributing to negative environmental effects during fertirrigation and/or to the obstruction of bioethanol fermentation.
We measured chemical characteristics and extracted total DNA from six vinasse batches taken over 1.5 years from a bioethanol and sugar mill in Sao Paulo State. The vinasse microbial assemblage was characterized by low alpha diversity with 5-15 species across the six vinasses. The core genus was . The top six represented bacterial genera across the samples were , and (Phylum Firmicutes, 35-97% of sample reads); and (Phylum Proteobacteria, 0-40%); (Phylum Bacteroidetes, 0-53%); and (Phylum Actinobacteria, 0-18%). Potential genes for denitrification but not nitrification were identified in the vinasse metagenomes, with putative K and Z genes the most represented. Binning resulted in 38 large bins with between 36.0 and 99.3% completeness, and five small mobile element bins. Of the large bins, 53% could be classified at the phylum level as Firmicutes, 15% as Proteobacteria, 13% as unknown phyla, 13% as Bacteroidetes and 6% as Actinobacteria. The large bins spanned a range of potential denitrifiers; moreover, the genetic repertoires of all the large bins included the presence of genes involved in acetate, CO, ethanol, HO, and lactose metabolism; for many of the large bins, genes related to the metabolism of mannitol, xylose, butyric acid, cellulose, sucrose, "3-hydroxy" fatty acids and antibiotic resistance were present based on the annotations. In total, 21 vinasse bacterial draft genomes were submitted to the genome repository.
Identification of the gene repertoires of vinasse bacteria and assemblages supported the idea that organic carbon and nitrogen present in vinasse together with microbiological variation of vinasse might lead to varying patterns of NO emissions during fertirrigation. Furthermore, we uncovered draft genomes of novel strains of known bioethanol contaminants, as well as draft genomes unknown at the phylum level. This study will aid efforts to improve bioethanol production efficiency and sugarcane agriculture sustainability.
从甘蔗中生产1升乙醇会产生多达12升的酒糟，这是一种含有尚未明确特征的微生物群落的液体废物。由于酒糟中含有高含量的有机物质和钾，大多数酒糟被用作甘蔗田的肥料；然而，当酒糟与无机氮肥共同施用时，会观察到一氧化氮排放量增加。在这里，我们旨在表征酒糟的微生物群落，以确定酒糟微生物在施肥灌溉过程中导致负面环境影响和/或阻碍生物乙醇发酵的基因潜力。
我们测量了化学特性，并从圣保罗州一家生物乙醇和制糖厂在1.5年期间采集的六个酒糟批次中提取了总DNA。酒糟微生物群落的特点是α多样性较低，六个酒糟样本中共有5 - 15个物种。核心属是 。样本中排名前六位的细菌属分别是 、 和 （厚壁菌门，占样本读数的35 - 97%）； 和 （变形菌门，占0 - 40%）； （拟杆菌门，占0 - 53%）；以及 （放线菌门，占0 - 18%）。在酒糟宏基因组中鉴定出了反硝化但不是硝化的潜在基因，其中假定的K和Z基因最为常见。分箱操作产生了38个大型箱，完整性在36.0%至99.3%之间，以及5个小型移动元件箱。在大型箱中，53%在门水平上可归类为厚壁菌门，15%为变形菌门，13%为未知门，13%为拟杆菌门，6%为放线菌门。大型箱涵盖了一系列潜在的反硝化菌；此外，所有大型箱的基因库都包括参与乙酸盐、一氧化碳、乙醇、水和乳糖代谢的基因；根据注释，对于许多大型箱，还存在与甘露醇、木糖、丁酸、纤维素、蔗糖、“羟基”脂肪酸代谢和抗生素抗性相关的基因。总共向基因组库提交了21个酒糟细菌草图基因组。
酒糟细菌和群落的基因库鉴定支持了这样一种观点，即酒糟中存在的有机碳和氮以及酒糟的微生物变化可能导致施肥灌溉过程中一氧化氮排放模式的变化。此外，我们发现了已知生物乙醇污染物新菌株的草图基因组，以及门水平上未知的草图基因组。这项研究将有助于提高生物乙醇生产效率和甘蔗农业可持续性。
