Statistical and sequential (fill-and-draw) approach to enhance rhamnolipid production using industrial lignocellulosic hydrolysate C6 stream from Achromobacter sp. (PS1)

The production of rhamnolipid from Achromobacter sp. (PS1) was statistically optimized using industrial lignocellulosic hydrolysate C6 stream containing 5.0% total sugars and further improved by adopting a sequential fermentation approach with fill-and-draw operation. Response surface methodology was used to statistically optimize the medium containing lignocellulosic hydrolyzed sugars along with other parameters as sodium nitrate, yeast extract, ferrous sulphate, phosphate concentrations and agitation under a six variable central composite design. The experimental rhamnolipid yield of 5.46 g/L was obtained at optimum conditions of total sugars 40 g/L(w/v), sodium nitrate 6.0 (g/L), yeast extract 2 (g/L), ferrous sulphate 0.2 (mg/L) and phosphate 1000mM at 100 rpm at 30°C in 8 days. The sequential approach with fill-and-draw operation, resulted in an overall yield of 19.35 g/L in five sequential cycles with an increase of 258% in rhamnolipid yield over the batch process due to replenishment of nutrients and dilution of toxic byproducts.