Secretomics: a biochemical footprinting tool for developing microalgal cultivation strategies.

Microalgae offer a promising source of biofuel and a wide array of high-value biomolecules. Large-scale cultivation of microalgae at low density poses a significant challenge in terms of water management. High-density microalgae cultivation, however, can be challenging due to biochemical changes associated with growth dynamics. Therefore, there is a need for a biomarker that can predict the optimum density for high biomass cultivation. A locally isolated microalga Cyanobacterium aponinum CCC734 was grown with optimized nitrogen and phosphorus in the ratio of 12:1 for sustained high biomass productivity. To understand density-associated bottlenecks secretome dynamics were monitored at biomass densities from 0.6 ± 0.1 to 7 ± 0.1 g/L (2 to 22 OD) in batch mode. Liquid chromatography coupled with mass spectrometry identified 880 exometabolites in the supernatant of C. aponinum CCC734. The PCA analysis showed similarity between exometabolite profiles at low (4 and 8 OD) and mid (12 and 16 OD), whereas distinctly separate at high biomass concentrations (20 and 22 OD). Ten exometabolites were selected based on their role in influencing growth and are specifically present at low, mid, and high biomass concentrations. Taking cues from secretome dynamics, 5.0 ± 0.5 g/L biomass concentration (16 OD) was optimal for C. aponinum CCC734 cultivation. Further validation was performed with a semi-turbidostat mode of cultivation for 29 days with a volumetric productivity of 1.0 ± 0.2 g/L/day. The secretomes-based footprinting tool is the first comprehensive growth study of exometabolite at the molecular level at variable biomass densities. This tool may be utilized in analyzing and directing microalgal cultivation strategies and reduction in overall operating costs.

Characterization of nanocellulose production by strains of Komagataeibacter sp. isolated from organic waste and Kombucha.

Bacterial nanocellulose production is gaining popularity owing to its applications in food, cosmetics and medical industry. Three Acetobacter strains isolated from organic waste and fermented tea were identified using 16S rDNA sequencing and their ability to produce nanocellulose was studied. Strain isolated from Kombucha has 99% homology with Komagataeibacter rhaeticus DSM 16663 T. This is the first report where nanocellulose productivity of this strain with different carbon sources such as glucose, glycerol, fructose and sucrose has been studied. 1% glycerol was found to be optimal concentration, with up to 69% of the utilized carbon converted to nanocellulose. Maximum productivity of 4.5 g/L of bacterial nanocellulose was obtained. Average nitrogen and phosphorus consumption rate was 45 mg/L/day each. Physical properties such as crystallinity, fibril dimensions, and glass transition temperature were studied. Bacterial cellulose was 80% crystalline when glycerol and glucose were used as carbon source and 73% for fructose and sucrose. Renewable materials such as bacterial cellulose with their unique properties are the future for applications in the field of cosmetics, composite and wound care.