Enhancing Lactic Acid Tolerance and Sophorolipids Production of Starmerella Bombicola by Atmospheric and Room-Temperature Plasma (ARTP) and Adaptive Laboratory Evolution (ALE)

Biosurfactants have recently garnered augmented attention due to their remarkable attributes compared with their fossil-derived counterparts. Despite the broad spectrum of applications, SLs production cost remains the principal impediment in outperforming synthetic surfactants. Although the integration of secondary feedstocks such as food waste presents a potential avenue for enhancing the sustainability of SLs production, the utilization of such feedstocks remains limited due to the potential inhibitors in these feedstocks.

In this study, different methods were used to address the inhibitors effect in food waste. Firstly, the inhibitory effect of lactic acid (LA) on yeast strain Starmerella bombicola was investigated. Then a combination of Atmospheric and Room-Temperature Plasma (ARTP) mutagenesis and Adaptive Laboratory Evolution (ALE) was employed to breed the LA-tolerant strain. The mutants that underwent prolonged LA pressure domestication exhibited enhanced cell growth. Furthermore, there were corresponding changes in cell morphology, along with an increase in cell membrane formation. In addition, LA-tolerant strains with higher SL yield were obtained after two rounds of screening, and their SL productivity was verified by food waste fermentation. Finally, resequencing and transcriptome were employed to analyze the mutants' internal changes in response to LA stress. This work provides valuable insights for facilitating direct utilization of food waste in SLs production, which can reduce the energy and resource consumption associated with the pretreatment process.