Organic chemistry

Rhamnolipid

Growth medium

Bacteria

Biology

Fermentation

Micelle

Laboratory flask

Bioreactor

Aqueous solution

Chemistry

Corn steep liquor

Pseudomonas aeruginosa

Glycerol

Burkholderia

Food science

Genetics

Biochemistry

Critical micelle concentration

Applied Microbiology and Biotechnology

The agro-industrial by-products corn steep liquor (CSL) and olive mill wastewater (OMW) were evaluated as low-cost substrates for rhamnolipid production by Burkholderia thailandensis E264. In a culture medium containing CSL (7.5% (v/v)) as sole substrate, B. thailandensis E264 produced 175 mg rhamnolipid/L, which is about 1.3 times the amount produced in the standard medium, which contains glycerol, peptone, and meat extract. When the CSL medium was supplemented with OMW (10% (v/v)), rhamnolipid production further increased up to 253 mg/L in flasks and 269 mg/L in a bioreactor. Rhamnolipids produced in CSL + OMW medium reduced the surface tension up to 27.1 mN/m, with a critical micelle concentration of 51 mg/L, better than the values obtained with the standard medium (28.9 mN/m and 58 mg/L, respectively). However, rhamnolipids produced in CSL + OMW medium displayed a weak emulsifying activity when compared to those produced in the other media. Whereas di-rhamnolipid congeners represented between 90 and 95% of rhamnolipids produced by B. thailandensis E264 in CSL and the standard medium, the relative abundance of mono-rhamnolipids increased up to 55% in the culture medium containing OMW. The difference in the rhamnolipid congeners produced in each medium explains their different surface-active properties. To the best of our knowledge, this is the first report of rhamnolipid production by B. thailandensis using a culture medium containing agro-industrial by-products as sole ingredients. Furthermore, rhamnolipids produced in the different media recovered around 60% of crude oil from contaminated sand, demonstrating its potential application in the petroleum industry and bioremediation. • B. thailandensis produced RL using agro-industrial by-products as sole substrates • Purified RL displayed excellent surface activity (minimum surface tension 27mN/m) • Crude RL (cell-free supernatant) recovered 60% of crude oil from contaminated sand

Cost-effective rhamnolipid production by Burkholderia thailandensis E264 using agro-industrial residues