Butyric acid as sole product from xylose fermentation by a non-solventogenic Clostridium beijerinckii strain under controlled pH and nutritional conditions

• Published in: Bioresource technology reports 2020-06, Vol.10, p.100426, Article 100426
• Main Authors: Fonseca, Bruna Constante, Bortolucci, Jonatã, da Silva, Thalita Marques, dos Passos, Vinícius Fabiano, de Gouvêa, Paula Fagundes, Dinamarco, Taísa Magnani, Reginatto, Valeria
• Format: Article
• Language: English
• Subjects: Acetate kinase; Butyrate kinase; C/N ratio; Non-dissociated acid; Organic acids
• ISSN: 2589-014X; 2589-014X
• DOI: 10.1016/j.biteb.2020.100426

Fermentative processes allow butyric acid to be produced from renewable substrates, which makes this compound commercially attractive. We have employed the non-solventogenic C. beijerinckii strain Br21 to obtain butyric acid from xylose under different nutritional conditions and controlled pH. Reinforced Clostridium Medium (RCM), which has the lowest C/N ratio, provided the highest butyrate/acetate ratio. When the RCM pH was kept at 6.5, butyric acid was the sole product of xylose fermentation by strain Br21. The butyric acid concentration was 5.2 times higher as compared to the fermentation without controlled pH. The genes buk (butyrate kinase) and hyd (hydrogenase) had their expressions enhanced by 6.8 and 2.0 times during the maximal acid production phase. On the other hand, ack (acetate kinase) had its expression weakened by 2.2 times under controlled pH. C. beijerinckii Br21 is a promising strain for highly specific butyric acid production from substrates derived from lignocellulose. [Display omitted] •C. beijerinckii has not been seen as a potential butyric acid producer.•The absence of gene adc in strain Br21 promotes butyric acid accumulation.•The lowest C/N ratios provides the highest xylose conversion into butyric acid.•pH control enhances xylose consumption and butyric acid production.•pH control prevents ack and enhances buk gene level expression.