Mesophilic fermentation upgrades SCFA production from natural/raw henna plant biomass

Henna ( Lawsonia inermis ) plant biomass is a popular source of natural dye lawsone used all over the world. In this study, the effect of temperature on fermentative production of short-chain fatty acids (SCFA) from raw henna biomass was investigated. The results indicated that mesophilic fermentation (35 °C) upgraded the SCFA production as compared with those under normal (25 °C) and thermophilic (25 °C) conditions, increasing by up to 2.2-fold and 1.5-fold, respectively. Acetic acid was the main SCFA component, accounting for 50 ~ 70% of the total SCFA, and followed by n -butyric acid and propionic acid. The enzymatic activities of α-glucosidase in thermophilic series were lower than those in mesophilic series, resulting in a less carbohydrate consumption and SCFA production. Soluble lawsone was positively correlated with fermentation temperature; and the average concentration (87.0 mg/L) in mesophilic series was appropriate to serve as a redox mediator to improve the acidification process for SCFA production. Future work to systematically scrutinize the confounding factors affecting the fermentation process of henna biomass was required. Graphical abstract