Prospective Life Cycle Assessment of Microbial Sophorolipid Fermentation

Description

Refinery industry is transitioning from fossil and chemical-based processes to more sustainable practices emphasizing renewable resources. Sophorolipids, a promising group of biosurfactants, present a viable substitute for conventionally produced surfactants. This study focuses on life cycle assessment (LCA) of the microbial sophorolipid fermentation.
The fermentation was done in a 5L lab-scale bioreactor, using yeast Starmerella bombicola (DSM 27465 strain), and raw rapeseed oil as a lipid substrate. Prospective LCA methodology was employed to identify environmental hotspots of the process. The hotspots that had a significant environmental impact (>1%) were addressed. The identified hotspots were electricity consumption (85.1%) and lipid source in fermentation substrate, namely raw rapeseed oil (14.2%). In terms of damage categories, the LCA results showed that human health is significantly impacted by electricity consumption due to the release of particulate matter during the combustion of solid biofuels in power plants. Meanwhile, ecosystems receive most of the damage from the use of raw rapeseed oil through land use change, agricultural practices, and potential chemical inputs, affecting biodiversity, soil health, and water resources. The environmental impact of the production can be reduced through optimization. This can include selecting a different substrate, improving technologies, and adjusting growth parameters to reduce electricity consumption. In this study, we proposed and assessed alternative scenarios to minimize the impact, such as using waste cooking oil instead of raw rapeseed oil, energy saving measures, and maximised use of bioreactor working volume.
To reduce electricity consumption (kWh per 1 kg of produced sophorolipids), we considered shortening the fermentation process, utilizing the maximum working volume of a lab-scale bioreactor chamber, and increasing energy efficiency of the process by measures such as lower temperature, reduced mixing speed or reduced heat loss from the process. LCA results showed that longer fermentation time resulted in 150% higher environmental impact, as the experimentally obtained sophorolipid titre was lower. Utilizing the maximum working volume of the bioreactor reduces the environmental impact by nearly 5%. Meanwhile, increased energy efficiency by 5%, 10% and 15% yielded reduction in environmental impact by 4%, 7% and 11%, respectively.
Using waste cooking oil as the lipid source helps avoiding the environmental impact caused by raw rapeseed oil and allows achieving a 28% reduction in environmental impact of the fermentation process assuming that the sophorolipid titre is the same as for the base scenario, i.e., 196.3 g/L. If higher sophorolipid titre is achieved, as was demonstrated in our laboratory experiments, then the impact can be reduced by as much as 52%.
We assessed a hypothetical scenario that compiled the most environmentally favourable strategies. Specifically, achieving a 50% higher titre using waste cooking oil combined with maximised use of bioreactor working volume and a 15% reduction in electricity consumption would potentially lead to a 60% reduction of the environmental impact compared to the base scenario.
This research provides valuable insights into environmental optimization of fermentation. Through LCA application, it highlights potential reductions in the negative environmental impact of sophorolipid production.

Period	4 Oct 2023 → 5 Oct 2023
Event title	WIRE’s 4th Working Groups Workshop: Waste biorefinery technologies for accelerating sustainable energy processes
Event type	Workshop
Location	Cottbus, GermanyShow on map
Degree of Recognition	International