Caprylic acid enhances hydroxyhexylitaconic acid production in Aspergillus niger S17‐5.

Aim: Aspergillus niger S17‐5 produces two alkylitaconic acids, 9‐hydroxyhexylitaconic acid (9‐HHIA) and 10‐hydroxyhexylitaconic acid (10‐HHIA), which have cytotoxic and polymer building block properties. In this study, we characterized the production of 9‐HHIA and 10‐HHIA by addition of their expected precursor, caprylic acid, to a culture of A. niger S17‐5, and demonstrated batch fermentation of 9‐HHIA and 10‐HHIA in a jar fermenter with DO‐stat. Methods and Results: Production titres of 9‐HHIA and 10‐HHIA from 3% glucose in a flask after 25 days cultivation were 0·35 and 1·01 g l−1 respectively. Addition of 0·22 g l−1 of caprylic acid to a suspension of resting cells of A. niger S17‐5 led to 32% enhancement of total 9‐HHIA and 10‐HHIA production compared to no addition. No enhancement of the production of 9‐HHIA or 10‐HHIA by the addition of oxaloacetic acid was observed. Addition of caprylic acid to the culture at mid‐growth phase was more suitable for 9‐HHIA and 10‐HHIA production due to less cell growth inhibition by caprylic acid. DO‐stat batch fermentation with 3% glucose and 14·4 g l−1 of caprylic acid in a 1·5 l jar fermenter resulted in the production titres of 9‐HHIA and 10‐HHIA being 0·48 and 1·54 g l−1 respectively after 10 days of cultivation. Conclusions: Addition of caprylic acid to the culture of A. niger S17‐5 enhances 9‐HHIA and 10‐HHIA production. Significance and Impact of the Study: These results suggest that 9‐HHIA and 10‐HHIA are synthesized with octanoyl‐CoA derived from caprylic acid, and that the supply of octanoyl‐CoA is a rate‐limiting step in 9‐HHIA and 10‐HHIA production. To the best of our knowledge, this is the first report regarding the fermentation of naturally occurring itaconic acid derivatives in a jar fermenter. [ABSTRACT FROM AUTHOR]
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