ESTABLISHMENT OF A SIMPLE LACTOBACILLUS PLANTARUM CELL-CONSORTIUM FOR CELLULASE-XYLANASE SYNERGISTIC INTERACTIONS

Sarah Morais ¹ Naama Shterzer ² Inna Rozman Grinberg ³ Geir Mathiesen ⁴ Vincent GH Eijsink ⁴ Lars Axelsson ⁵ Raphael Lamed ³ Edward A. Bayer ¹ Itzhak Mizrahi Itzhak Mizrahi ²

¹Biological Chemistry, Weizmann Institute of Sciences, Rehovot
²Department of Ruminant Science, ARO, Bet Dagan
³Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv
⁴Department of Chemistry Biotechnology and Food Science, Norwegian University of Life Sciences, As
⁵Norwegian Institute of Food, Nofima, As

Lactobacillus plantarum is an attractive candidate for bioprocessing of lignocellulosic biomass due to its high metabolic variability, including its ability to ferment both pentoses and hexoses, as well as its high acid tolerance, a quality often utilized in industrial processes. This bacterium grows naturally on biomass; however, it lacks the inherent ability to deconstruct lignocellulosic substrates. As a first step towards engineering lignocelluloses-converting lactobacilli, we have introduced genes coding for a GH6 cellulase and a GH11 xylanase from a highly active cellulolytic bacterium into L. plantarum. For this purpose, we employed the recently developed pSIP vectors for efficient secretion of heterologous proteins. Both enzymes were secreted by L. plantarum, at levels estimated at 0.33 nM and 3.3 nM in OD600=1 culture, for the cellulase and xylanase, respectively. Transformed cells demonstrated the ability to degrade individually either cellulose or xylan and wheat straw. When mixed together to form a two-strain cell-based consortium secreting both cellulase and xylanase, they exhibited synergistic activity in the overall release of soluble sugar from wheat straw. This result paves the way towards metabolically harnessing of L. plantarum for novel biorefining applications, such as production of ethanol and polylactic acid directly from plant biomass.