A specific biocatalyst for a specific feedstock - production of platform chemicals from perennial rye grass by metabolically engineered Lactobacillus plantarum
Thursday, May 1, 2014: 9:45 AM
Grand Ballroom D-E, lobby level (Hilton Clearwater Beach)
Alun Thomas Hughes, David N Bryant and Joe A Gallagher, Institute of Biological Environmental and Rural Science, Aberystwyth University, Aberystwyth, United Kingdom
High sugar perennial rye grasses (HSPRGs) have been identified as potential biorefining feedstocks for the production of transport fuels and platform chemicals. These grasses are high yielding and contain high levels of water soluble carbohydrates (WSC), 25-30% of dry matter. The predominant WSC is the storage sugar fructan; a polysaccharide chain of fructose units.

The use of such feedstocks for the production of platform chemicals requires microbial biocatalysts capable of producing high value products at commercially viable yields from these sugars. The lactic acid bacterium (LAB), Lactobacillus plantarum strain Aber F1 isolated from HSPRG silages is capable of converting fructan into racemic lactic acid at high substrate and product concentrations. The Aber F1 genome has been sequenced and the enzyme for fructan utilisation has been identified as a fructan exohydrolase (FEH).

Work is underway to manipulate Lactobacillus metabolism to produce high levels of optically pure either (D) or (L) lactate rather than a racemic mix.  Aber F1 is however recalcitrant to genetic manipulation and efforts to transform this strain have been unsuccessful. While work continues on attempting to develop a functional transformation protocol for the Aber F1, the FEH is being integrated into the genome of a more genetically malleable strain, L. plantarum NC8 so it can utilise polymeric fructan.  A number of knockouts are being made initially in NC8, then in AberF1 to alter the route of carbon metabolism in the strains to produce optically pure lactate.