Biologically active secondary metabolites and biotechnological applications of species of the family Chaetomiaceae (Sordariales): an updated review from 2016 to 2021

Lignocellulosic biomass has long been recognized as a potential sustainable source of mixed sugars for fermentation to biofuels and other biomaterials. Several technologies have been developed during the past 80 years that allow this conversion process to occur, and the clear objective now is to make this process cost-competitive in today's markets. Here, we consider the natural resistance of plant cell walls to microbial and enzymatic deconstruction, collectively known as "biomass recalcitrance." It is this property of plants that is largely responsible for the high cost of lignocellulose conversion. To achieve sustainable energy production, it will be necessary to overcome the chemical and structural properties that have evolved in biomass to prevent its disassembly.

One of the exciting movements in microbial sciences has been a refocusing and revitalization of efforts to mine the fungal secondary metabolome. The magnitude of biosynthetic gene clusters (BGCs) in a single filamentous fungal genome combined with the historic number of sequenced genomes suggests that the secondary metabolite wealth of filamentous fungi is largely untapped. Mining algorithms and scalable expression platforms have greatly expanded access to the chemical repertoire of fungal-derived secondary metabolites. In this Review, I discuss new insights into the transcriptional and epigenetic regulation of BGCs and the ecological roles of fungal secondary metabolites in warfare, defence and development. I also explore avenues for the identification of new fungal metabolites and the challenges in harvesting fungal-derived secondary metabolites.

Pretreatment is an important step involved in the production of bioethanol from lignocelluosic biomass. Though several pretreatment regimes are available, biological pretreatment seems to be promising being an eco-friendly process and there is no inhibitor generation during the process. In the current scenario there are few limitations in using this strategy for pilot scale process. The first and foremost one is the long incubation time for effective delignification. This can be minimized to an extent by using suitable microbial consortium. There is an urgent need for research and development activities and fine tuning of the process for the development of an economically viable process. This review presents an overview of various aspects of biological pretreatment, enzymes involved in the process, parameters affecting biological pretreatment as well as future perspectives.