Identifying novel lignocellulosic processing enzymes from cellulomonas fimi using transcriptomic, proteomic and evolution adaptive studies

Abstract

The declining reserves of fossil fuel twined with an increasing concern about the environmental consequences of burning these fuels and rising carbon dioxide levels, means that a more sustainable replacement is required. Lignocellulosic biomass is an attractive candidate that has been shown to be the best sustainable alternative source to produce bioethanol for liquid transportation fuels. It has enormous availability, is renewable and cost-effective. As an agricultural residue, it does not compete with food production. However, lignocellulosic biomass of plant cell walls is composed mainly of cellulose, hemicellulose and lignin, which are extremely resistant to digestion. Converting this biomass to useful products of fermentable sugars for bioethanol production has met with little success as harsh pretreatment and costly enzyme applications are required. An arsenal of enzymes and a synergistic mechanism are required to deconstruct recalcitrant lignocellulosic biomass for an efficient production of lignocellulosic bioethanol. To achieve this goal, this study used transcriptomic and proteomic approaches with the objective of identifying new genes and enzymes involved in lignocellulose degradation. This revealed that the only one AA10 of Cellulomonas fimi was among the highest enzymes identified during the degradation of cellulose. Another other 20 hypothetical proteins co-expressed with CAZymes have been identified including a potentially exclusively new C. fimi β-glucosidase (PKDP1) that contains a PKD-domain and oxidoreductase predicted function of PQQ-domain. A naturally mutagenized C. fimi population also was screened from an adaptive evolution experiment involving exposure to a wheat straw environment. One of the strains in the adaptive population (Strain-6) showed a higher association with wheat straw biomass, which may be an indication of the strategy that being used by the adapted strain to tackle obstinate substrates to sustain growth. These results show many new enzymes would be revealed from the C. fimi repertoire in order to have a better enzymatic cocktails for lignocellulose breakdown. For the future, this encourages a deeper understanding of lignocellulose deconstruction mechanisms by an orchestra of multiple enzymes in a bacterial system.