Queensland University of Technology, 2 George St, Brisbane, QLD, 4000, Australia.
Metabolomics Australia, Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, St. Lucia, QLD, 4072, Australia.
BMC Biotechnol. 2020 Feb 28;20(1):12. doi: 10.1186/s12896-020-00609-y.
Sugarcane bagasse is a major source of lignocellulosic biomass, yet its economic potential is not fully realised. To add value to bagasse, processing is needed to gain access to the embodied recalcitrant biomaterials. When bagasse is stored in piles in the open for long periods it is colonised by microbes originating from the sugarcane, the soil nearby or spores in the environment. For these microorganisms to proliferate they must digest the bagasse to access carbon for growth. The microbial community in bagasse piles is thus a potential resource for the discovery of useful and novel microbes and industrial enzymes. We used culturing and metabarcoding to understand the diversity of microorganisms found in a uniquely undisturbed bagasse storage pile and screened the cultured organisms for fibre-degrading enzymes.
Samples collected from 60 to 80 cm deep in the bagasse pile showed hemicellulose and partial lignin degradation. One hundred and four microbes were cultured from different layers and included a high proportion of oleaginous yeast and biomass-degrading fungi. Overall, 70, 67, 70 and 57% of the microbes showed carboxy-methyl cellulase, xylanase, laccase and peroxidase activity, respectively. These percentages were higher in microbes selectively cultured from deep layers, with all four activities found for 44% of these organisms. Culturing and amplicon sequencing showed that there was less diversity and therefore more selection in the deeper layers, which were dominated by thermophiles and acid tolerant organisms, compared with the top of pile. Amplicon sequencing indicated that novel fungi were present in the pile.
A combination of culture-dependent and independent methods was successful in exploring the diversity in the bagasse pile. The variety of species that was found and that are known for biomass degradation shows that the bagasse pile was a valuable selective environment for the identification of new microbes and enzymes with biotechnological potential. In particular, lignin-modifying activities have not been reported previously for many of the species that were identified, suggesting future studies are warranted.
甘蔗渣是木质纤维素生物质的主要来源，但它的经济潜力尚未得到充分实现。为了提高甘蔗渣的附加值，需要对其进行加工，以获得其中所含的顽固性生物材料。当甘蔗渣在露天堆场中长时间储存时，会被来自甘蔗、附近土壤或环境中的孢子的微生物定植。为了繁殖，这些微生物必须消化甘蔗渣以获取生长所需的碳。因此，甘蔗渣堆中的微生物群落是发现有用和新颖微生物和工业酶的潜在资源。我们使用培养和代谢组学来了解在一个独特未受干扰的甘蔗渣储存堆中发现的微生物多样性，并筛选培养的微生物以获得纤维降解酶。
从甘蔗渣堆的 60 至 80 厘米深处采集的样本显示出半纤维素和部分木质素的降解。从不同层培养了 104 种微生物，其中包括高比例的油脂酵母和生物质降解真菌。总体而言，分别有 70%、67%、70%和 57%的微生物表现出羧甲基纤维素酶、木聚糖酶、漆酶和过氧化物酶活性。从深层选择性培养的微生物中，这些百分比更高，其中 44%的微生物具有这四种活性。培养和扩增子测序表明，与堆顶相比，深层的微生物多样性较低，选择压力更大，主要由嗜热菌和耐酸菌主导。扩增子测序表明，堆中存在新型真菌。
培养依赖和独立方法的结合成功地探索了甘蔗渣堆中的多样性。发现的物种多样性和已知的生物质降解物种表明，甘蔗渣堆是鉴定具有生物技术潜力的新微生物和酶的有价值的选择性环境。特别是，许多被鉴定的物种以前没有报道过木质素修饰活性，这表明未来有必要进行进一步研究。
