Mutation of Gluconobacter oxydans and Bacillus megaterium in a two-step process of l-ascorbic acid manufacture by ion beam

Abstract

Aim: To increase the transformation rate of l-sorbose to 2-keto-l-gulonic (2-KLG) acid in a two-step process of l-ascrobic acid manufacture by ion beam. Methods and Results: Gluconobacter oxydans (GO29) and Bacillus megaterium (BM80) were used in the present study. Ion implantation was carried out with the heavy ion implantation facility at the institute of Plasma Physics in China. 2-KLG in whole culture broth was determined by iodometry. Mutants were screened by single-colony isolation and 2-KLG accumulation in broth. GO29 and BM80 were implanted by either hydrogen ions (H⁺) or nitrogen ions (N⁺) with various doses, respectively. The average transformation rate of GM112-302 bred by ion beam in Gram-molecule was increased from 79·3 to 94·5% after eight passages in shaking flasks. Furthermore, in 180-ton fermentors in Jiangsu Jiangshan Pharmaceutical Co. Ltd, the transformation rate was stable at 92·0%, indicating a producer could get 0·99 kg of gulonic acid from 1·0 kg of sorbose. Conclusion: Ion beam as a new mutation source had potential advantages in breeding. Comparing with original mixture GO29 and BM80, GM112-302 is more efficient in accumulating 2-KLG, especially at the later phase. Significance and Impact of the Study: GM112-302 bred by ion beam implantation dramatically increased the transformation rate by 19·2%, which greatly increased efficiency and reduced the cost of l-ascorbic acid manufacture in a two-step process.