Maximizing biomass productivity of cyanobacterium Nostoc sp. through high-throughput bioprocess optimization and application in multiproduct biorefinery towards a holistic zero waste

Abstract

This study aimed to maximize the biomass productivity of cyanobacterium Nostoc sp. AARL C008 by high-throughput bioprocess optimization, and to utilize the Nostoc biomass for application in multiproduct biorefinery towards holistic zero-waste technology. Through bioprocess optimization, maximum biomass productivity was obtained as 37.59 mg/L/day under modified BG-11 medium (0.190 g/L K2HPO4·3H2O, 0.0018 g/L citric acid and 2.53 mL/L trace metal solution) and continuous light feeding at 40 µmol/m2/s. The zero-waste biorefining process was successfully used for Nostoc biomass to sequentially recover polysaccharides, phytochemicals, and lipids. Nostoc polysaccharides exhibited the bio-stimulant potential having the ability to improve soil properties such as moisture content, organic matter, microbiological activity, and cation exchange capacity by increases measured as 1.30, 1.55, 1.53, and 1.47-fold, respectively, compared to the control in which polysaccharides were absent. With 120 mg/L polysaccharides, the short length of melon was significantly enhanced 1.29-fold, higher than the control. After polysaccharide extraction, the cyanobacterial biomass residue (CBR) was used to extract the phytochemicals. Nostoc phytochemicals showed high antioxidant activity, giving ABTS activity of 26.10 mg TE/g-extract, DPPH activity of 5.71 mg GAE/g-extract, and PFRAP activity of 7.79 mg GAE/g-extract, as well as offering high-efficiency inhibitive effects on cancer cells with the IC50 recorded at 0.50 mg/mL. The CBR after phytochemical extraction can potentially be used to extract lipids prior to biodiesel production. The extracted lipid contained long-chain fatty acids with satisfactory fuel properties. The overall results evidenced that the multiproduct biorefining approach will make a significant contribution to the zero-waste industrialization of cyanobacterial-based bioproducts.