ARS | Publication request: Production of poly(beta-L-malic acid) (PMA) from agricultural biomass substrates by Aureobasidium pullulans

Submitted to: Biotechnology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 21, 2012
Publication Date: October 1, 2012
Citation: Leathers, T.D., Manitchotpisit, P. 2012. Production of poly(beta-L-malic acid) (PMA) from agricultural biomass substrates by Aureobasidium pullulans. Biotechnology Letters. 35(1):83-89.

Interpretive Summary: We demonstrate here for the first time the efficient utilization of agricultural biomass substrates, particularly corn fiber and wheat straw, for production of the valuable biopolyester, poly(beta-L-malic acid) (PMA). Utilization of biomass substrates for PMA production could provide a new value-added product from agricultural residues. We identified promising microbial strains and determined optimal conditions required for conversion of wheat straw to PMA. This work will be valuable to researchers developing new value-added bioproducts for the integrated biorefineries of the future.

Technical Abstract: We report here for the first time the production of poly(beta-L-malic acid) (PMA) from agricultural biomass substrates by the yeastlike fungus Aureobasidium pullulans. Strains NRRL Y 2311-1, NRRL 50382, NRRL 50383, and NRRL 50384, representing diverse isolation sources and phylogenetic clades, produced PMA from alkaline hydrogen peroxide-pretreated corn fiber and wheat straw as sole carbon sources. Pretreated wheat straw was a better substrate than pretreated corn fiber, and strain NRRL 50383 gave the highest overall yields of PMA. The addition of CaCO3 plus supplementary hydrolytic enzymes enhanced PMA production. Four basal media were compared for PMA production, and the best was found to be a nitrogen limited pullulan production medium (PM). In this medium, PMA production took place during growth limitation. Under optimal conditions, strain NRRL 50383 produced more than 20 g PMA/l from 5% (w/v) pretreated wheat straw in PM with 3% (w/v) CaCO3 and supplementary enzymes.