Unravelling the secrets of a landfill for municipal solid waste (MSW): Lipid-to-biodiesel production by the new strain Chlorella vulgaris DSAF isolated from leachates

Abstract

The unceasing rise in human population has provoked large environmental damage, essentially in air and water habitats. Microalgae have been deeply investigated regarding wastewater treatment as well as a suitable biofuel feedstock. Nevertheless, process optimization and the search for new local strains are imperative to overcome the cost-effectiveness bottleneck that persist in large-scale technology. Linked to this, micro-diversity studies in landfill leachates have been done. However, there has been no study which analysed specifically the microalgal diversity outside of this less-explored environment to see their biotechnological potential. Hence, a specific study of microalgal diversity present in leachates produced by a non-hazardous waste landfill (mainly for municipal solid waste MSW) located in Asturias (Spain) was done. The new strain Chlorella vulgaris DSAF was isolated and identified based on both morphological and molecular methods. Some parameters based on site-climate conditions were studied to understand C. vulgaris DSAF behaviour. The modification in the lipid content and FAMEs profile in response to the stress caused by the addition of NaCl and nutrient deprivation were also studied. The stress induction produced significant morphological changes when compared to control group (e.g., bigger cell sizes). Specifically, the addition of 25 g L^-1 of NaCl achieved an increase of 25% of biomass. Total lipids increased under nutrient deprivation (N, P and NP) from 13 to 34% (w/w). Oleic acid was the most abundant fatty acid, reaching 50% of total FAMEs under NP deprivation conditions. Linoleic acid and α-linolenic acid also showed a moderate increase during NaCl stress. The positive results during calculation of the main biodiesel properties determined that C. vulgaris DSAF would be a potential biodiesel feedstock under different cultivation conditions.