title: Enhanced succinic acid production in Aspergillus saccharolyticus by heterologous expression of fumarate reductase from Trypanosoma brucei.
abstract: Aspergillus saccharolyticus exhibits great potential as a cell factory for industrial production of dicarboxylic acids. In the analysis of the organic acid profile, A. saccharolyticus was cultivated in an acid production medium using two different pH conditions. The specific activities of the enzymes, pyruvate carboxylase (PYC), malate dehydrogenase (MDH), and fumarase (FUM), involved in the reductive tricarboxylic acid (rTCA) branch, were examined and compared in cells harvested from the acid production medium and a complete medium. The results showed that ambient pH had a significant impact on the pattern and the amount of organic acids produced by A. saccharolyticus. The wild-type strain produced higher amount of malic acid and succinic acid in the pH buffered condition (pH 6.5) compared with the pH non-buffered condition. The enzyme assays showed that the rTCA branch was active in the acid production medium as well as the complete medium, but the measured enzyme activities were different depending on the media. Furthermore, a soluble NADH-dependent fumarate reductase gene (frd) from Trypanosoma brucei was inserted and expressed in A. saccharolyticus. The expression of the frd gene led to an enhanced production of succinic acid in frd transformants compared with the wild-type in both pH buffered and pH non-buffered conditions with highest amount produced in the pH buffered condition (16.2 ± 0.5 g/L). This study demonstrates the feasibility of increasing succinic acid production through the cytosolic reductive pathway by genetic engineering in A. saccharolyticus.
authors.affiliation: Section for Sustainable Biotechnology, Department of Chemistry and Bioscience, Aalborg University Copenhagen, A. C. Meyers Vaenge 15, DK-2450, Copenhagen SV, Denmark.
authors.forename: Lei
authors.initials: L
authors.lastname: Yang
authors.affiliation: Section for Sustainable Biotechnology, Department of Chemistry and Bioscience, Aalborg University Copenhagen, A. C. Meyers Vaenge 15, DK-2450, Copenhagen SV, Denmark.
authors.forename: Mette
authors.initials: M
authors.lastname: Lübeck
authors.affiliation: Section for Sustainable Biotechnology, Department of Chemistry and Bioscience, Aalborg University Copenhagen, A. C. Meyers Vaenge 15, DK-2450, Copenhagen SV, Denmark.|Bioproducts, Sciences & Engineering Laboratory (BSEL), Washington State University, Tri-Cities, 2710 Crimson Way, Richland, WA, 99354, USA.
authors.forename: Birgitte K
authors.initials: BK
authors.lastname: Ahring
authors.affiliation: Section for Sustainable Biotechnology, Department of Chemistry and Bioscience, Aalborg University Copenhagen, A. C. Meyers Vaenge 15, DK-2450, Copenhagen SV, Denmark. psl@bio.aau.dk.
authors.forename: Peter S
authors.initials: PS
authors.lastname: Lübeck
mesh_terms: D001230:Aspergillus / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D015870:Gene Expression; D006863:Hydrogen-Ion Concentration; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013385:Succinate Dehydrogenase / Q000235:genetics* / Q000378:metabolism*; D019802:Succinic Acid / Q000378:metabolism*; D014346:Trypanosoma brucei brucei / Q000201:enzymology* / Q000235:genetics
chemical_list: D003470:Culture Media; D011994:Recombinant Proteins; D019802:Succinic Acid; D013385:Succinate Dehydrogenase
keywords: Aspergillus saccharolyticus; Fumarate reductase; Genetic engineering; Malic acid; Succinic acid