Fungal-assisted harvesting of Chlorella sorokiniana cultivated in diluted anaerobic digestate using the edible mushroom Pleurotus ostreatus.

Abstract

The use of fungi as a bio-flocculant for microalgae harvesting has gained great attention in recent years. However, most of the examined fungi were pathogenic, making the harvested biomass unsuitable for human or animal consumption. In the present study, the effectiveness of the edible fungal strain Pleurotus ostreatus was tested for harvesting microalgae Chlorella sorokiniana, cultivated in diluted anaerobic digestate. Types of fungal pellets, pH values, and harvesting durations were examined as critical parameters for harvesting efficiency. The results showed that the maximum harvesting efficiency (74%) at pH 4.5 was achieved using large-sized fungal pellets (formed after 9 days) and extended harvesting periods (24 h). In contrast, at pH 5.5, the highest harvesting efficiencies (68-69%) were observed with medium-sized fungal pellets (formed after 7 days) after 6 h of contact time or with small-sized fungal pellets (formed after 5 days) after 24 h of contact time. The composition of the harvested fungal-algal biomass slightly differed at pH 4.5 compared to pH 5.5. Specifically, it contained a significant amount of proteins (40-45%) and carbohydrates (33-36%) along with approximately 4-5% of fatty acids, mainly linoleic acid, palmitic acid, and stearic acid. Overall, the use of fungal pellets produced by the edible fungus P. ostreatus appears to be a promising option for producing harvested fungal-algal biomass suitable for use as food or animal feed.