Abstract
β-poly(l-malic acid) (PMLA) is a water-soluble biopolymer used in medicine, food, and other industries. However, the low level of PMLA biosynthesis in microorganisms limits its further application in the biotechnological industry. In this study, corn steep liquor (CSL), which processes high nutritional value and low-cost characteristics, was selected as a growth factor to increase the PMLA production in strain, Aureobasidium melanogenum, and its metabolomics change under the CSL addition was investigated. The results indicated that, with 3 g/L CSL, PMLA production, cell growth, and yield (Yp/x) were increased by 32.76%, 41.82%, and 47.43%, respectively. The intracellular metabolites of A. melanogenum, such as amino acids, organic acids, and key intermediates in the TCA cycle, increased after the addition of CSL, and the enrichment analysis showed that tyrosine may play a major role in the PMLA biosynthesis. The results presented in this study demonstrated that the addition of CSL would be an efficient approach to improve PMLA production.
Highlights
Polymalic acid (PMLA) is a polyester of l-malic acid with a wide range of applications in the medical, food, and environmental industries due to its excellent biochemical properties, including biocompatibility, biodegradability, and chemical modifiability (Zeng et al 2019)
Metabolomics analysis of poly(l-malic acid) (PMLA) metabolic pathway The metabolic pathway related to PMLA biosynthesis and the relative concentration changes were depicted (Fig. 5)
The maximal PMLA production and biomass increased by 32.76% and 41.82%, respectively
Summary
Polymalic acid (PMLA) is a polyester of l-malic acid with a wide range of applications in the medical, food, and environmental industries due to its excellent biochemical properties, including biocompatibility, biodegradability, and chemical modifiability (Zeng et al 2019). Regardless of the microorganism used in PMLA production, l-malic acid is the only precursor in PMLA biosynthesis (Zeng et al 2019). The three major metabolic pathways in PMLA biosynthesis are the tricarboxylic acid cycle (TCA), reductive TCA (rTCA), and glyoxylate pathway (Chi et al 2016). Several factors were tested to increase PMLA production, including the screening of mutant strains, optimizing fermentation conditions, selecting suitable carbon sources, and adding growth factors (Cao et al 2019a, b). The researcher speculated that the metabolic pathway of PMLA may vary in different strains. The research found that PMLA production is considerably associated with
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