A method for simultaneous bioflocculation and pretreatment of algal biomass targeting improved methane production

Abstract

A novel method for simultaneous bioflocculation and pretreatment of algae is revealed. The method includes bioflocculation of precultured algae (Chroococcus sp.) using pellet forming filamentous fungus (Aspergillus lentulusFJ172995) resulting in nearly 100% harvesting within 6 h without addition of any nutrient and carbon source at the optimized fungal/algal (F/A) ratio of 1:3. The algal-fungal interactions require metabolically active fungus with opposite charge. The bioflocculation process is replicable at reactor scale under continuous aeration. Simple incubation of harvested algal-fungal pellets under controlled conditions was associated with significant cellulase production (> 0.4 FPU mL -1 ) by the fungus leading to soluble sugar release ( ≈ 360 mg L -1 ) from algal cells. As a result, > 54% enhancement in digestibility and marked increase in methane production (up to 50 %) from algal fungal pellets during anaerobic digestion was noticed. The invention is a unique process of its kind and has potential application in algae based biofuel production including biomethane, biohydrogen and biodiesel as well as in extraction of valuables from microalgal biomass.

Potential role of N-acetyl glucosamine in Aspergillus fumigatus-assisted Chlorella pyrenoidosa harvesting

“…The present study can be closely related to the above-mentioned cases as it also reports extracellular secretions from A. fumigatus , mediating cell wall changes in the C. pyrenoidosa cells. These secretions might help A. fumigatus to provide signal to the C. pyrenoidosa cell and bring it into close vicinity for nutritional benefits or enzymatic degradation [32]. Similar phenomenon of microalgal–fungal attachment has been reported by our group with wide range of microalgal species encompassing green algae ( Chlorella sp.…”

“…Apart from biodiesel aspect, harvesting of microalgae using filamentous fungi also increases its biogas potential. Prajapati et al [32] reported enhanced bio-methane production from algal–fungal pellets due to the enzymatic degradation of microalgal cell wall by the fungi. All these studies show that harvesting algae with filamentous fungi is a favorable process for biofuel production.…”

“…However, the studies with co-cultivation of fungi and algae have reported the interaction time to be between 24 and 72 h [22, 25–31]. In a more straight-forward approach, it has been observed that the attachment of algal cells (green algae or cyanobacteria) to fungal pellets could take place within 4–6 h using pre-cultivated fungal biomass [12, 32]. Such interaction of algae and PFF [12] is intriguing as it does not follow the simple kinetics of bio-harvesting [13, 33, 34].…”

“…Relatively simple phytoplankton–parasitic fungal (Chytrids) interactions controlled by cell-to-cell contact also exist in nature, which are driven by chemotaxis [37]. In our recent studies, somewhat similar action of fungus was observed in algal–fungal pellets as fungus used algal cells as nutrient source by enzymatically degrading it [32]. However, what drives the interaction between C. pyrenoidosa and A. fumigatus at the molecular level is not clear.…”

The effect of the algal microbiome on industrial production of microalgae

“…Furthermore, algal-fungal copelletization improved oil extraction efficiency because fungal secreted hydrolytic enzymes disrupted the thick cell walls of Tetraselmis suecica (Muradov et al, 2015). The same was seen between Aspergillus lentulus FJ172995 and Chroococcus sp., where algal and fungal cells formed a pellet, and nearly 100% of biomass settled down within 6 h at an optimized fungal/algal ratio of 1:3 (Prajapati et al, 2016).…”