Optimized production of biosurfactant from Pseudozyma tsukubaensis using cassava wastewater and consecutive production of galactooligosaccharides: An integrated process

This study aimed to produce biosurfactant from Pseudozyma tsukubaensis using cassava wastewater and an inoculum (biomass) for galactooligosaccharides synthesis from lactose as an integrated system. First, the use of cassava wastewater as a low cost culture medium by P. tsukubaensis to produce biomass and biosurfactant was evaluated and optimized. Then, the microbial cells (biomass) obtained from the optimized process were used to produce galactooligosaccharides from lactose. The optimum conditions for biosurfactant and biomass synthesis were found to be 80% (v/v) of cassava wastewater at 30 °C and 200 rpm for 48 h. The highest concentration of biosurfactant, that is, minimum surface tension value and maximum biomass concentration predicted were experimentally confirmed as 26.87 mN/m and 10.5 g/L, respectively. The biosurfactant obtained showed good thermal (121 °C/1 h), pH (2–11) and ionic strength (0–25% NaCl) stability. Excellent emulsifier activity was also verified, suggesting a potential application in enhanced oil recovery. Galactooligosaccharides synthesized by the Kluyveromyces genus have been extensively investigated, however, few studies have reported transgalactosylation ability by other yeast genera. The transgalactosylation activity of the yeast biomass at optimized conditions from 40% (w/w) lactose resulted in galactooligosaccharides production of 73.12 g/L and a yield of 18.28% (w/w) at pH 8.0 and 30 °C in 24 h. This research showed the technical feasibility of an integrated process: biosurfactant and GOS production from P. tsukubaensis, which takes advantage of the remarkable metabolism of this microorganism. To the best of our knowledge, this is the first study reporting the potential of P. tsukubaensis to produce two economical biotechnological products of increase interest as an integrated process.