Biosynthesis of polymalic acid in fermentation: advances and prospects for industrial application

Abstract

Some microorganisms naturally produce β-poly(l-malic acid) (PMA), which has excellent water solubility, biodegradability, and biocompatibility properties. PMA has broad prospective applications as novel biopolymeric materials and carriers in the drug, food, and biomedical fields. Malic acid, a four-carbon dicarboxylic acid, is widely used in foods and pharmaceuticals, as a platform chemical. Currently, malic acid produced through chemical synthesis and is available as a racemic mixture of l- and d-forms. The d-form malic acid exhibits safety concerns for human consumption. There is extensive interest to develop economical bioprocesses for l-malic acid and PMA production from renewable biomass feedstocks. In this review, we focus on PMA biosynthesis by Aureobasidium pullulans, a black yeast with a large genome containing genes encoding many hydrolases capable of degrading various plant materials. The metabolic and regulatory pathways for PMA biosynthesis, metabolic engineering strategies for strain development, process factors affecting fermentation kinetics and PMA production, and downstream processing for PMA recovery and purification are discussed. Prospects of microbial PMA and malic acid production are also considered.

Keywords:

• Aureobasidium pullulans
• biopolymer
• biosynthesis
• malic acid
• metabolic engineering
• polymalic acid
• yeast

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [Grant Nos. 31571816 and 31871783], the United Soybean Board [USB-1426], the National High Technology Research and Development Program of China (863 Program) [2015AA021005], Chongqing Social and People's Livelihood Guarantee Special Program [cstc2016shmszx80075], and Fundamental Research Funds for the Central Universities [XDJK2018AC002].