Algal Bioproducts Research Articles

Optimization of cationic amino starch synthesis using biogenic amines

Harvesting microalgae presents a challenge in selecting the most economical method for low cost algal bioproducts. Previous studies have shown coagulation–flocculation to be the most efficient method for large scale microalgae harvesting. This study focused on modifying native potato starch with biogenic amines and optimizing the reaction parameters. Such modification rendered the starch cationic, with an ability to destabilize microalgae suspensions or colloids. The effect of time, temperature, and reactant concentrations on the zeta potential of the cationic amino starch was studied. Biogenic amines including putrescine, histamine, cadaverine, and tyramine were selected for study based on the number of nitrogen groups in their structure. Zeta potential for histamine cationic amino starch was significantly higher (+9.0±2.0mV) at lower reaction temperatures, regardless of the amine to starch ratio and reaction time intervals. Putrescine, cadaverine, and tyramine cationic amino starches exhibited significantly higher zeta potential values (13.76±3.60, 6.81±1.64, and 5.68±1.60mV, respectively) with amine to starch ratio higher than reaction stoichiometry, irrespective of reaction temperature or time intervals. This optimization study has presented a basis for designing reaction conditions for the synthesis of cationic amino starch from an inhomogeneous mix of biogenic amines derived from waste sources.

Algal bioproducts derived from suspended solids in intensive land-based aquaculture

Land-based aquaculture produces suspended solids in culture pond and settlement pond waters that could be harvested as a bioresource. Suspended solids were quantified, characterised and harvested from these two sources to assess their suitability for conversion to bioproducts. The suspended solids of settlement ponds were less concentrated (87.6±24.7mgL−1) than those of culture ponds (131.8±8.8mgL−1), but had a higher concentration of microalgae (27.5±4.0%) and consequently higher particulate organic carbon (24.8±4.7%) and particulate nitrogen (4.0±0.8%). The microalgal community also differed between sources with a higher concentration of fatty acids in the biomass from settlement ponds. Consequently, biochar produced from biomass harvested from settlement ponds was higher in organic carbon and nitrogen, with a lower cation exchange capacity. In conclusion, we characterised a renewable and potentially valuable bioresource for algal bioproducts derived from suspended solids in intensive land-based aquaculture.