Microbial lignocellulolytic secretome analysis using metatranscriptomics and proteomics techniques for enzyme discovery

Due to world’s population increase, the modern life more and more dependent on electricity and the economical development of undeveloped countries, the world’s energy consumption is growing at an accelerated rate. In Brazil, for example, the energy consumption has grown 50% from 1996 to 2010 (1). The growing energetic demand and the necessity of diversifying the energy matrix combined with concerns about the environment make it clear that we can no longer depend on non-renewable energy sources. Lignocellulosic plant biomass can potentially be used to produce second-generation ethanol. However, at the moment, this process is not economically viable as a result of pretreatment, transportation and enzyme production costs (2). While the saccharification of biomass remains a problem for industry, microbial communities carry it out effectively in nature. Yet, as less than 1% of microorganisms are amenable to cultivation, this saccharification has been studied for only a few model organisms so far (3). In this work, we aim to characterize new Carbohydrate-Active Enzymes (CAZymes) that break biomass more efficiently and potentially at lower costs. The research takes an integrated proteomics and metatranscriptomics approach to study a microbial community from a composting system. The community was grown in minimal medium supplemented with sugar-cane bagasse and the proteomics and metatranscriptomics was analyzed weekly for 5 weeks. 2,939 CAZymes were identified out of 215,388 assembled transcripts. From those, 1,708 had no BLAST hit to any PDB protein. A number of enzymes are being selected now for high-throughput cloning and characterization.