Abstract
Oxalic acid is formed by Aspergillus niger at nearly neutral pH values. In this study the applicability of milk whey as a carbon source was investigated, both in shaking flask experiments and in a stirred tank reactor. The influence of pH on oxalic acid formation showed that the maximum production rate and higher concentration of the product are observed at pH 6. At pH 7 the same production rate was obtained although at a lower oxalic acid concentration. The process was shown to be inhibited by product from an oxalic acid concentration of about 10 kg/m3 and its behaviour was fitted by Luong's equation. In a 10-dm3 strirred tank ferment the stirrer speed was varied in a range from 100 to 600 rpm. At values between 200 and 400 rpm, maximum production rates of oxalic acid of 6.8 kg/m3·d and 6.5 kg/m3·d were reached, respec-tively. A final concentration of 41.4 kg oxalic acid/m3 was reached operating at 400 rpm.
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Received: 27 October 1997
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Bohlmann, J., Cameselle, C., Nunez, M. et al. Oxalic acid production by Aspergillus niger . Bioprocess Engineering 19, 337–342 (1998). https://doi.org/10.1007/PL00009022
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DOI: https://doi.org/10.1007/PL00009022