Abstract
Bacterial and algal floc formation was induced by inoculating three species of wastewater-derived bacteria (Melaminivora jejuensis, Comamonas flocculans, and Escherichia coli) into algal cultures (Chlorella sorokiniana). Bacterial and algal flocs formed in algal cultures inoculated with M. jejuensis and C. flocculans, and these flocs showed higher sedimentation rates than pure algal culture. The floc formed by M. jejuensis (4988.46 ± 2589.81 μm) was 10-fold larger than the floc formed by C. flocculans (488.60 ± 226.22 μm), with a three-fold higher sedimentation rate (M. jejuensis, 91.08 ± 2.32% and C. flocculans, 32.55 ± 6.33%). Biomass and lipid productivity were improved with M. jejuensis inoculation [biomass, 102.25 ± 0.35 mg/(L·day) and 57.80 ± 0.20 mg/(L·day)] compared with the productivity obtained under pure algal culture conditions [biomass, 78.00 ± 3.89 mg/(L·day) and lipids, 42.26 ± 2.11 mg/(L·day)]. Furthermore, the fatty acid composition of the biomass produced under pure algal culture conditions was mainly composed of C16:0 (43.67%) and C18:2 (45.99%), whereas the fatty acid composition of the biomass produced by M. jejuensis was mainly C16:0 (31.80%), C16:1 (24.45%), C18:1 (20.23%), and C18:2 (16.11%). These results suggest the possibility of developing an efficient method for harvesting microalgae using M. jejuensis and provide information on how to improve biomass productivity using floc-forming bacteria.
Highlights
Microalgae are a source of bioenergy raw material that can be used to produce biofuels
We suggest that M. jejuensis has the potential to flocculate more efficiently than C. flocculans and E. coli
We demonstrated the value of bacterial- and algalderived biomass for improving the harvesting efficiency using bacterial and algal floc
Summary
Microalgae are a source of bioenergy raw material that can be used to produce biofuels. This unique bioresource has been proposed as a solution to combat energy shortages and alleviate problems associated with global warming (Morales et al, 2019; Tan et al, 2019). The biomass produced through microalgae cultivation is harvested using processes such as centrifugation and filtration (Dassey and Theegala, 2013; Farooq et al, 2013). Significant losses and production costs are incurred during harvest (Dassey and Theegala, 2013; Farooq et al, 2013). Solutions to reduce the losses and production costs associated with harvesting processes are essential (Jonker and Faaij, 2013)
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