Molecular characterization of cellulase genes in Pseudomonas stutzeri

Abstract

Background: Cellulose is one of the most abundant natural sources of carbon. In biofuel manufacturing, cellulase is used as an enzyme to hydrolyze cellulose into a fermentable product (glucose). Pseudomonas stutzeri is one of the microorganisms found in cattle rumen. The microbiome of the rumen is heterogeneous and known for its potentiality to efficiently hydrolyze cellulose. Recent studies have identified, cloned, and crystallized one of the cellulase genes present in P. stutzeri, the A1501 cellulase gene (PST_2494 gene).

Results: This study describes the isolation of cellulase-producing bacteria from sheep's rumen. The highest cellulase-producing isolate was identified as P. stutzeri by 16s rDNA sequencing. qRT-PCR was used to measure the cellulase gene expression levels, revealing a higher gene expression of the PST_1459 gene (4 folds) compared to PST_2494 genes. Moreover, cellulase productivity was enhanced by UV irradiation mutagenesis.

Conclusions: Sheep's rumen bacterial isolates were tested for their cellulase productivity, and the highest was identified as P. stutzeri. An investigation of the cellulase genes of P. stutzeri revealed the presence of an unidentified cellulase gene (PST_1459). A qRT-PCR reaction was carried out to validate and measure the expression levels of different cellulase genes, revealing a higher gene expression of the PST_1459 gene than PST_2494 genes. Moreover, UV irradiation mutagenesis was performed to enhance cellulase productivity. The gene expression tested by qRT-PCR confirmed the enhancement of cellulase productivity in some of the mutants obtained.