Unraveling the extracellular polysaccharide utilization system of Cellulomonas sp

TOPALIAN, JULIANA; OÑATON, ORNELLA; VALACCO MARIA PIA,; CAMPOS, ELEONORA

virtual

Simposio; 43rd Symposium on Biomaterials, Fuels and Chemicals; 2021

Society for Industrial Microbiology and Biotechnology

One of the main features of species from Cellulomonas genus is their ability to secrete (hemi)cellulolytic enzymes. We have studied the exo-proteome of two Cellulomonas isolates, Cellulomonas sp. B6, and C. fimi B-402 when grown on different lignocellulosic carbon sources and the genetic distribution of the genes encoding for the secreted proteins. Both isolates presented mainly xylanase activity, although the highest activity was observed by growth on different substrates: wheat bran (WB) for Cellulomonas sp. B6 (3.5 IUxyn/ml) and waste paper (WP) for C. fimi (1.5 IUxyn/ml). By mass spectrometry analysis of the extracellular fractions, we identified 31 and 26 GHs (out of 195 and 348 total proteins detected) in Cellulomonas sp. B6 and C. fimi, respectively. In the Cellulomonas sp. B6 WB extracellular extract, 2 GH10 xylanases and a GH62 alpha-L-arabinofuranosidase were amongst the most abundant proteins. In C. fimi, a single GH10 xylanase was the most abundant protein. In both extracts, a high abundance of extracellular proteins from ABC sugar transport systems was observed. Most CAZymes were encoded in distant regions of the genome, with few exceptions. In Cellulomonas sp. B6, we identified a cluster encoding a GH43 and a GH10 and both enzymes were detected in WB-secretome. In C. fimi, a GH10 and a GH62 identified in the secretome were encoded along with the sequence for a GH43. A common feature observed was the presence of coding sequences for sugar transporters (mainly ABC family) and transcriptional regulators along with genes encoding CAZymes. In summary, Cellulomonas sp. can secrete xylanases and other glycosyl-hydrolases with different relative abundance when cultured in lignocellulosic substrates. The coding sequences for these proteins are distributed along the genome, mostly surrounded by sequences encoding different transcriptional regulators and transporter systems.