Paenibacillus barengoltzii A1_50L2 as a Source of Plant Cell Wall Degrading Enzymes and Its Use on Lignocellulosic Biomass Hydrolysis

Lignocellulosic residues daily generated as a by-product of economic activities worldwide, stand out as potential feedstock to biorefineries. Industrial processes based on their use still face a challenge in the development of low-cost enzymatic mixtures resistant to inhibitors produced during pre-treatment step and efficient in the complete deconstruction of different lignocellulosic wastes. In the present work, Paenibacillus barengoltzii A1_50L2 isolated from bovine rumen was studied as a source of plant cell wall degrading enzymes. In addition, the natural produced enzymatic cocktail was characterized and applied to the hydrolysis of lignocellulosic substrates. P. barengoltzii grew in liquid media containing cellulose, sugarcane bagasse and wheat bran, as carbon source producing endo-1,4-β-xylanases, pectinases, mannanases, endo-1,4-β-glucanases, exo-1,4-β-glucanases and β-glucosidases, with highest values of endo-1,4-β-xylanase activity. Six isoforms of endo-1,4-β-xylanase (45 to 116 kDa), three of endo-1,4-β-glucanase (40 to 66 kDa) and a single band of mannanase (62 kDa) were secreted by the bacterium during growth on wheat bran, all enzymes presented maximal activity in pH ranging from 4 up to 8 and temperature from 45 up to 60 °C. Endo-1,4-β-xylanases, endo-1,4-β-glucanases, exo-1,4-β-glucanases, pectinases, mannanases and β-glucosidases produced by P. barengoltzii are tolerant to lignin-derived compounds showing a minimal residual activity of 61%. Ferulic, gallic, tannic and cinnamic acids enhanced activities of endo-1,4-β-glucanases/endo-1,4-β-xylanases, mannanase and pectinase, respectively. P. barengoltzii enzymatic cocktail (PbEC) hydrolyzes sugarcane bagasse, banana stem and corncob with hydrolysis values comparable to those obtained for the commercial blend Viscozyme®. The addition of PbEC to Viscozyme® increases the hydrolysis rate of sugarcane bagasse, banana stem and corncob in three to four times.