Vibrational spectroscopy monitoring of microalgae-fungi co-cultures as a strategy to microalgae-based lipid production

Microalgae commercialization is limited to high value products due to a high production cost. To reduce it, harvesting of microalgae biomass should be improved (20% to 50% of the cost). For this purpose, the co-cultivation of fungi and microalgae has been reported as a promising strategy as fungi can aggregate microalgae through flocculation or pellet formation. Furthermore, the co-culturing may improve the lipid yields compared to monoculture. A few species combinations have been investigated so far while their efficiency is strain dependent. Moreover, most of the investigated fungi are non-oleaginous, and often lower the lipid yield as their biomass is predominant. In this study we report a proof-of-concept for co-culturing microalgae oleaginous fungus for increased lipid production and easier harvesting of algae biomass. Further, there is a need for a robust and high-throughput method allowing to estimate biochemical composition of the co-culture. In this regard, vibrational spectroscopy is particularly useful as it can provide a total biochemical fingerprint spectrum, specific to each microorganism, which allows to evaluate the biomass content and the ratio of microorganisms in the co-culture. In this study, we also report on how vibrational spectroscopy can be used to identify the content of fungi-microalgae co-cultures. We used different strains of microalgae, yeast, and filamentous fungi in monoculture. Their dry biomass was mixed (filamentous fungi or yeast with microalgae) and analysed with vibrational spectroscopy. A model is created with the spectra obtained and used to evaluate the ratio of each organism in a co-culture and their lipid content.