Enhanced acid tolerance of Rhizopus oryzae during fumaric acid production
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Ensuring a suitable pH in the culture broth is a major problem in microorganism-assisted industrial fermentation of organic acids. To address this issue, we investigated the physiological changes in Rhizopus oryzae at different extracellular pH levels and attempted to solve the issue of cell shortage under low pH conditions. We compared various parameters, such as membrane fatty acids’ composition, intracellular pH, and adenosine triphosphate (ATP) concentration. It was found that the shortage of intracellular ATP might be the main reason for the low rate of fumaric acid production by R. oryzae under low pH conditions. When 1 g/l citrate was added to the culture medium at pH 3.0, the intracellular ATP concentration increased from 0.4 to 0.7 µmol/mg, and the fumaric acid titer was enhanced by 63 % compared with the control (pH 3.0 without citrate addition). The final fumaric acid concentration at pH 3.0 reached 21.9 g/l after 96 h of fermentation. This strategy is simple and feasible for industrial fumaric acid production under low pH conditions.
KeywordsRhizopus oryzae Fumaric acid Low pH fermentation Acid tolerance ATP
This work was financially supported by the National Natural Science Foundation of China (No. 21106065), the National Basic Research Program of China (No. 2013CB733605), National Science Foundation for Distinguished Young Scholars of China (No. 21225626), and the National High Technology Research and Development Program of China (No. 2011AA02A206).
- 3.Roa Engel CA (2010) Integration of fermentation and cooling crystallisation to produce organic acids[D]. Delft University of Technology, The Netherlands, pp 46–63Google Scholar
- 13.Xu S, Zhou J, Qin Y, Liu L, Chen J (2010) Water-forming NADH oxidase protects Torulopsis glabrata against hyperosmotic stress. Yeast 27:207–216Google Scholar
- 16.McElhaney RN, Souza KA (1976) The relationship between environmental temperature, cell growth and the fluidity and physical state of the membrane lipids in Bacillus stearothermophilus. Biochim Biophysica Acta (BBA) Biomembranes 443:348–359Google Scholar