Microalgal research has made significant progress due to versatile and high‐value industrial applications of microalgal biomass or its derivatives. However, to explore their full potential and to achieve commercial robustness, microalgal biorefinery needs cost‐effective technologies to produce, harvest, and process the microalgal biomass on large scale as higher production and harvesting cost is one of the key hindrances in the commercialization of algae‐based products. Among several other algal biomass harvesting technologies, self‐flocculation seems to be an attractive, low‐cost, and eco‐friendly harvesting technology. This review covers various flocculation‐based methods that have been employed to harvest microalgal biomass with a special emphasis on self‐flocculation in microalgae. Moreover, genetic engineering approaches to induce self‐flocculation in non‐flocculating microalgae along with the factors affecting self‐flocculation and recent research trends have also been discussed. It is concluded that self‐flocculation is the most desired approach for the energy‐ and environment‐efficient harvesting of microalgal biomass. However, its poorly understood genetic basis needs to be deciphered through detailed studies to harness its potential for the algal biorefinery.
The cultivation of Plectonema terebrans BERC10 in wastewater and integrating the wastewater-derived biomass followed by its processing for multiple products in a biorefinery could help in achieving environmental sustainability and cost effectiveness. This study evaluated the resource recovery potential of the cyanobacterium Plectonema terebrans BERC10 from urban wastewater followed by the cascading processing of the biomass into multiple bioproducts. The annual biomass productivity ranged from 0.035–0.064 gL−1d−1 and contained 40–46% lipids and 20–38% protein. The cascading processing of the biomass resulted in multiple products, including 53 mgg−1 of high-value pigments and high-quality biodiesel in accordance with American and European standards. The pigment-free and de-fatted residual biomass was used as a sole feedstock (30–70 gL−1) to produce enzymes and mycoproteins via fungal fermentation employing Aspergillus niger and Aspergillus oryzae. Interestingly, A. oryzae produced 28 UmL−1 of α-amylase and the final residues were mycoproteins after 96 h. Furthermore, the strain removed 80–90% of total phosphorous, 90–99% of total nitrogen, and significantly lowered the COD, BOD, and TDS of urban wastewater. The data demonstrated that P. terebrans has substantial potential for resource recovery and could become a candidate for a wastewater-derived algal biorefinery.
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