Engineering Aspergillus oryzae for high level production of L-malic acid

Debbie S Yaver, S. Brown, A. Berry

Author address: 

Expression Technology, Novozymes, Inc., Davis, CA


In the last decade, there has been widespread interest and investment in developing processes for the production of bulk and specialty chemicals from renewable feedstocks by fermentation. During this period, Novozymes has successfully developed technology for production of a specialty molecule (hyaluronic acid) by Bacillus fermentation and has been very active in developing technologies for the production of bulk chemicals by metabolic engineering and fermentation using several different microorganisms. An example of the latter is L-malic acid. In the literature it is reported that some wild-type Aspergillus strains produce high levels of malic acid under specific cultivation conditions. Concentrations up to 113 g/L malate (94% w/w from glucose) reported for A. flavus in fed-batch fermentations (Battat, et. al., 1991. Biotechnol. Bioeng. 37:1108-1116). The goal of our work was to improve malic acid production in the natural malic acid producing filamentous fungus Aspergillus oryzae NRRL 3488 by overexpression of cloned genes and classical mutagenesis. More than 75 different recombinant strains were tested containing combinations of overexpression of genes as well as deletions. A high through put screen was developed and used to screen mutagenized strains. Combined genetic engineering and mutagenesis/HTS was used to increase the malic acid production rate of A. oryzae NRRL3488 by 4-fold with final C4 acid totals of 340 g/l at 8 days in lab scale fermentations.

abstract No: 


Full conference title: 

27th Fungal Genetics Conference
    • Fungal Genetics Conference 27th (2013)