Fermentative production of l-galactonate by using recombinant Saccharomyces cerevisiae containing the endogenous galacturonate reductase gene from Cryptococcus diffluens

• Published in: Journal of bioscience and bioengineering Vol. 122; no. 5; pp. 639 - 644
• Main Authors: Matsubara, Takeo, Hamada, Shohei, Wakabayashi, Ayaka, Kishida, Masao
• Format: Journal Article
• Language: English
• Published: Japan Elsevier B.V 01.11.2016
• Subjects: Aerobiosis; Cryptococcus - enzymology; Cryptococcus - genetics; Cryptococcus diffluens; d-Galacturonate; Fermentation - genetics; Galacturonate reductase; Hexuronic Acids - metabolism; l-Galactonate; NAD (+) and NADP (+) Dependent Alcohol Oxidoreductases - genetics; NAD (+) and NADP (+) Dependent Alcohol Oxidoreductases - metabolism; Organisms, Genetically Modified; Saccharomyces cerevisiae; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Sugar Acids - metabolism; Galacturonate reductase; d-Galacturonate; Saccharomyces cerevisiae; l-Galactonate; Cryptococcus diffluens
• ISSN: 1389-1723; 1347-4421
• DOI: 10.1016/j.jbiosc.2016.05.002

The GAR1 gene, encoding d-galacturonate reductase in Cryptococcus diffluens, was isolated, and the GAR1-expression plasmid was constructed by insertion of GAR1 downstream of the yeast constitutive promoter in the yeast-integrating vector. Recombinant Saccharomyces cerevisiae expressing C. diffluensd-galacturonate reductase from a genome integrated copy of the gene was cultured for use the conversion of d-galacturonic acid to l-galactonic acid. The optimum conditions for l-galactonic acid production were determined in terms of the initial concentration of d-galacturonic acid, fermentation pH, and mixed sugars. The following conditions yielded high efficiency in the conversion of d-galacturonic acid to l-galactonic acid in large-scale cultures: 0.1% initial d-galacturonic acid concentration, pH 3.5, and glucose as additional sugar. The aerobic condition was necessary for the conversion of d-galacturonic acid. Subculture of that recombinant was not showing to decrease of the d-galacturonic acid conversion rate even though it was repeated in ten generations. Culturing in scale-up, the conversion rate of d-galacturonic acid to l-galactonic acid was increased.