Production and characterization of glycolipid biosurfactant from Achromobacter sp. (PS1) isolate using one-factor-at-a-time (OFAT) approach with feasible utilization of ammonia-soaked lignocellulosic pretreated residues.

With the ever growing increase in the demands of biosurfactants, the present study was focused in developing a set of parameters influencing biosurfactant production using one-factor-at-a-time (OFAT) approach in chemically defined medium from an indigenous isolate of Achromobacter sp. (PS1). Subsequently, the feasibility of biosurfactant production was examined using influential OFAT parameters in same medium, replacing only carbon source with lignocellulosic hydrolyzed sugars. These sugars were obtained from ammonia (15% v/v) soaking pretreatment of lignocellulosic residues (7.5% solid loading at 70 °C for 72 h) with subsequent saccharification using lignocellulolytic enzymes. OFAT influential parameters observed were dextrose (3-4% w/v); C/N ratio 8.3 using sodium nitrate and beef extract; 2 × 10 grams equivalents Fe; 1500 mM PO in minimal salt medium (MSM) at pH 7.0, 120 rpm, 30 °C resulting in 4.13 ± 0.12 g/L rhamnolipid in 192 h with 30.42 mN/m surface tension and 136 mg/L critical micelle concentration (CMC). Biosurfactant was characterized using tandem-MS and NMR as rhamnolipid with six-congeners, Rha-C-C and Rha-Rha-C-C being the most abundant. Rhamnolipid showed broad range stability at temperatures (30-121 °C), pH (6-12), and salinity (0.5-5% w/v) of NaCl. In Rice-straw (RS) hydrolysate, maximum glucan (73.10%) and xylan (91.13%) were obtained and the RS-hydrolysate medium with a total of 4.55% (w/v) sugars under optimum OFAT parameters (other than dextrose) showed at par production of 3.55 ± 0.06 g/L of rhamnolipid in 192 h with Y (biosurfactant yield per gram of sugar consumed) of 0.08 g/g and Y (biosurfactant yield per gram of cell biomass) of 0.68 g/g.