Identification of Corn Chaff as an Optimal Substrate for the Production of Rhamnolipids in Pseudomonas aeruginosa Fermentations

Waste biomass deriving from agricultural activities has different destinations depending on the possibility of applying it to specific processes. As the waste biomass is abundant, cheap, and generally safe, it can be used for several applications, biogas production being the most relevant from the quantitative point of view. In this study, we have used a set of agricultural by-products (agro-waste) deriving from the post-harvest treatment of cereals and legumes as the growth substrate for selected biosurfactant-producing microbial strains. The agricultural by-products were easily metabolized and highly effective for the growth of microorganisms and the production of rhamnolipids and surfactin by Pseudomonas aeruginosa and Bacillus subtilis, respectively. In particular, the use of corn chaff (“bee-wings”) was suitable for the production of rhamnolipids. Indeed, in corn-chaff-based media, rhamnolipids yields ranged from 2 to 18 g/L of fermentation broth. This study demonstrated that the use of waste raw materials could be applied to reduce the carbon footprint of the production of biosurfactants without compromising the possibility of having a suitable fermentation medium for industrial production.