Abstract
BackgroundBioflocculation has been developed as a cost-effective and environment-friendly method to harvest multiple microalgae. However, the high production cost of bioflocculants makes it difficult to scale up. In the current study, low-cost bioflocculants were produced from untreated corn stover by a biomass-degrading bacterium Pseudomonas sp. GO2.ResultsPseudomonas sp. GO2 showed excellent production ability of bioflocculants through directly hydrolyzing various biomasses. The untreated corn stover was selected as carbon source for bioflocculants’ production due to its highest flocculating efficiency compared to that when using other biomasses as carbon source. The effects of fermentation parameters on bioflocculants’ production were optimized via response surface methodology. According to the optimal model, an ideal flocculating efficiency of 99.8% was obtained with the fermentation time of 130.46 h, initial pH of 7.46, and biomass content of 0.64%. The relative importance of carboxymethyl cellulase and xylanase accounted for 51.8% in the process of bioflocculants’ production by boosted regression tree analysis, further indicating that the bioflocculants were mainly from the hydrolysates of biomass. Biochemical analysis showed that it contained 59.0% polysaccharides with uronic acid (34.2%), 32.1% protein, and 6.1% nucleic acid in the bioflocculants, which had an average molecular weight as 1.33 × 106 Da. In addition, the bioflocculants showed the highest flocculating efficiency at a concentration of 12.5 mg L−1 and were stable over broad ranges of pH and temperature. The highest flocculating efficiencies obtained for Chlorella zofingiensis and Neochloris oleoabundans were 77.9 and 88.9%, respectively.ConclusionsThe results indicated that Pseudomonas sp. GO2 can directly utilize various untreated lignocellulolytic biomasses to produce low-cost bioflocculants, which showed the high efficiency to harvest two green microalgae in a low GO2 fermentation broth/algal culture ratio.
Highlights
Bioflocculation has been developed as a cost-effective and environment-friendly method to harvest multiple microalgae
Most organic flocculants are mainly derived from fossil fuels or edible crops, which may further aggravate the problems of fossil fuel and food shortages, and associated environmental risks [5, 16]
Similar halo regions can be formed with the halo diameters of 2.8 and 2.7 cm in the agar plates containing carboxymethyl cellulose (CMC) and xylan, respectively, indicating the strain GO2 was capable of degrading the biomass through secreting carboxymethyl cellulase (CMCase) and xylanase [28, 29]
Summary
Bioflocculation has been developed as a cost-effective and environment-friendly method to harvest multiple microalgae. Costs may increase according to the size of microalgal cells, the density of the algal culture, and the intensity of negative charge on the surface of algae [7]. High-capital equipment and operational costs, high energy consumption, or heavy dependence on algal species have hampered large-scale commercialization of these microalgal harvesting methods [5, 12]. The harvest of microalgae through flocculation, which can form heavy aggregates by neutralizing the algal surface’s negative charges using various flocculants and increase the rate of settling [13], has been proposed as the most reliable and suitable harvesting method for multiple algae species, even at low biomass concentrations [6, 14]. Most organic flocculants are mainly derived from fossil fuels or edible crops, which may further aggravate the problems of fossil fuel and food shortages, and associated environmental risks [5, 16]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
