Enhancement of harvesting efficiency and polyunsaturated fatty acid-rich lipid production of Aurantiochytrium sp. SW1 by co-cultivation with oleaginous fungus Cunninghamella bainieri 2A1

Aims@#Thraustochytrids have been shown to be excellent lipid producers due to their ability to accumulate over 50% lipid (g/g biomass) containing up to 50% docosahexaenoic acid (DHA). However, efficient and cost-effective cell recovery of lipid-rich biomass has become a significant challenge at the industrial scale. In this study, we attempted to enhance the harvesting efficiency (HE) and the DHA content of Aurantiochytrium sp. through co-cultivation with a γ-linolenic acid (GLA)-producing oleaginous filamentous fungus, Cunninghamella bainieri 2A1.@*Methodology and results@#A 72 h old C. bainieri 2A1 culture in the form of loose mycelia or pellets of various sizes was added into 72 h old Aurantiochytrium sp. cultures and further incubated for 48 h. The HE of Aurantiochytrium sp. was then determined by comparing the remaining OD values of the supernatant with and without minimal centrifugation at 4000× g. Results showed that 63.23% of HE was achieved without centrifugation from co-cultivation with dispersed mycelia. Higher HE between 96.71-99.55% was achieved when centrifugation was implemented, with the highest value resulting from co-cultivation with dispersed mycelia. These are higher than HE of centrifuged control cultures (80%) consisting of Aurantiochytrium sp. monocultures, suggesting that co-cultivation with C. bainieri 2A1 facilitates the recovery of Aurantiochytrium sp. cells. Moreover, the co-cultivation also resulted in a 28% increase in DHA compared to non-optimized cultures.@*Conclusion, significance and impact of study@#This study provides the first evidence of enhancement in harvesting and DHA content of oleaginous thraustochytrids that could be achieved through co-cultivation with oleaginous fungi.

Efficiency of chitosan and eggshell on harvesting of Spirulina sp. in a bioflocculation process

Aims@#Microalgae were very small in size (a few μm) and have a low concentration in the medium. Due to their size, harvesting of microalgae from their growth medium remain a major obstacle in downstream processing. Efficient harvesting method must be applied to ensure it is cost effective, preserves quality and improves the culture process which is important for commercial algal production. Common harvesting methods use to harvest microalgae from their growth medium are centrifugation, filtration, flotation, sedimentation, and flocculation. Flocculation is a common method use to harvest microalgae due to low cost, save time and highly efficient method for algae biomass recovery. The purpose of this study was to investigate the effects chitosan and eggshell on flocculation of microalga Spirulina platensis. Chitosan and eggshell were chosen as flocculant due to their biodegradability, non-toxicity and safe to handle. @*Methodology and results@#The efficiencies of flocculation process were examined by conducting experiments over a range of culture pH, flocculant concentrations and flocculation time using chitosan and eggshell as flocculant agent. Under optimized flocculation conditions of 50 mg/L chitosan at pH 8 culture media for 90 min of flocculation time and 4 mg/mL eggshell at pH 4 culture media for 8 min of flocculation time, the maximum flocculation efficiency obtained was 79.98±1.65% and 97.17±1.38%, respectively. @*Conclusion, significance and impact of study@#Therefore, it can be concluded that chitosan and eggshell could be used as flocculants for harvesting large scale microalgal biomass production. Nevertheless, eggshell is more economical and more efficient compared to chitosan in harvesting microalgae biomass.