Potential of <i>Dictyosphaerium</i>sp. LC172264 Concomitant Remediation of Cassava Wastewater and Accumulation of Lipids for Biodiesel Production

As a way of making algal feedstock feasible for biofuel production, simultaneous utilization of microalga Dictyosphaerium sp. LC172264 for cassava wastewater remediation and accumulation of lipids for biodiesel production was investigated. The algal biomass, lipid contents and composition were measured from the autotrophic, heterotrophic and mixotrophic cultured algal cells. Physicochemical parameters of the cassava wastewater and bioremediation potentials were measured. Biodiesel properties were deduced and compared with the standards. The results showed that mixotrophic culture was the best for both biomass accumulation (1.022 g/L) and lipid contents (24.53%). Irrespective of the culture condition, the predominant fatty acids were similar and included 11-Octadecenoic acid (vaccenic acid (C19H36O2), oleic acid (C18H34O2) and 14-methyl pentadecanoic acid (isopalmitic acid (C17H34O2). The percentage reduction of total dissolved solids was 79.32% and 89.78% for heterotrophy and mixotrophy respectively. Biochemical oxygen demand was 72.95% and 89.35%, chemical oxygen demand was 72.19% and 84.03% whereas cyanide contents reduced from the initial value of 450 mg/L to 93.105 (79.31%) and 85.365 mg/L (81.03%) respectively. Dictyosphaerium sp. showed good growth and lipid production under mixotrophic condition and produced good quality biodiesel under the three cultivation modes. Even though both mixotrophic and heterotrophic conditions had good promise of cassava wastewater remediation by Dictyosphaerium sp., mixotrophy showed superiority.

Reaction-controlled microgel-lipase co-stabilized compartmentalized emulsion for recyclable biodiesel production

Pickering emulsions have been widely used for biphasic catalysis in the past decade.However,it remains a great challenge to achieve simple product collection and enzyme recovery.Poly(N-isopropylacrylamide)(PNIPAM)-based microgels can endow Pickering emulsions with stimuli-responsiveness,while most microgelstabilized emulsions are oil-in-water(O/W)type and not ideal for interfacial catalysis.Besides,altering temperature or pH value for demulsification is time-and energy-consuming and may cause irreversible deactivation of enzymes.In this work,inverse water-in-oil(W/O)Pickering emulsions were formed using hexanoic acidswollen microgels as the sole emulsifiers.When lipase was added in the water phase,stable oil-in-water-in-oil(O/W/O)Pickering double emulsions could be formed through one-step emulsification,owing to the synergistic effect of the hydrophobic microgels and hydrophilic lipase at the interface.Compared with other biphasic systems,such double emulsion systems represent a desirable platform for highly efficient biodiesel production because of the ultra-high interfacial areas and fast mass transport between two phases.More importantly,the switchable transition between hydrophobicity/hydrophilicity of microgels is controlled by the catalytic reaction.Therefore,double emulsions demulsify spontaneously when substrates are used up without the need for energy input or loss of enzymatic activity,enabling the facile collection of products and demonstrating the excellent recyclability of the biphasic catalysis system.