Ashik Sathish

Biodiesel from mixed culture algae via a wet lipid extraction procedure

Microalgae are a source of renewable oil for liquid fuels. However, costs for dewatering/drying, extraction, and processing have limited commercial scale production of biodiesel from algal biomass. A wet lipid extraction procedure was developed that was capable of extracting 79% of transesterifiable lipids from wet algal biomass (84% moisture) via acid and base hydrolysis (90 °C and ambient pressures), and 76% of those extracted lipids were isolated, by further processing, and converted to FAMEs. Furthermore, the procedure was capable of removing chlorophyll contamination of the algal lipid extract through precipitation. In addition, the procedure generated side streams that serve as feedstocks for microbial conversion to additional bioproducts. The capability of the procedure to extract lipids from wet algal biomass, to reduce/remove chlorophyll contamination, to potentially reduce organic solvent demand, and to generate feedstocks for high-value bioproducts presents opportunities to reduce costs of scaling up algal lipid extraction for biodiesel production.

Effect of coagulant/flocculants on bioproducts from microalgae

The potential of microalgae as a source of sustainable energy, nutritional supplements and specialized chemicals necessitates a thorough evaluation of the methods of harvesting microalgae with regards to the bioproduct(s) desired. This research assessed the effect of coagulation, flocculation, and centrifugation on the wet lipid extraction procedure, which fractionated microalgae into hydrolyzed biomass for fermentation into acetone, butanol, and ethanol, an aqueous phase as growth media for genetically engineered Escherichia coli, and a lipid fraction for the production of biodiesel. Biomass harvested by cationic starches, alum, and centrifugation produced 30, 19, and 22.5mg/g of dry wt. algae of total combined acetone, butanol, and ethanol, respectively. Higher biodiesel production was also observed for the cationic starches (9.6 mg/g of dry wt. algae) than alum (0.6 mg/g of dry wt. algae) harvested biomass. The results suggested significant effect of the harvesting methods on the yields of bioproducts.

Optimization of a wet microalgal lipid extraction procedure for improved lipid recovery for biofuel and bioproduct production

Methods to convert microalgal biomass to bio based fuels and chemicals are limited by several processing and economic hurdles. Research conducted in this study modified/optimized a previously published procedure capable of extracting transesterifiable lipids from wet algal biomass. This optimization resulted in the extraction of 77% of the total transesterifiable lipids, while reducing the amount of materials and temperature required in the procedure. In addition, characterization of side streams generated demonstrated that: (1) the C/N ratio of the residual biomass or lipid extracted (LE) biomass increased to 54.6 versus 10.1 for the original biomass, (2) the aqueous phase generated contains nitrogen, phosphorous, and carbon, and (3) the solid precipitate phase was composed of up to 11.2 wt% nitrogen (70% protein). The ability to isolate algal lipids and the possibility of utilizing generated side streams as products and/or feedstock material for downstream processes helps promote the algal biorefinery concept.

Effects of wastewater microalgae harvesting methods on polyhydroxybutyrate production.

Microalgae have gained considerable attention recently as a sustainable means to produce biofuels and bioproducts. It has previously been demonstrated that single strain microalgae can be harvested and processed through a wet lipid extraction procedure (WLEP). After WLEP processing, acetone, butanol, ethanol, and biodiesel can be produced, and growth of recombinant Escherichia coli can be achieved from the microalgae. This study demonstrates the application of different wastewater microalgae harvesting techniques and processing through WLEP on the production of polyhydroxybutyrate (PHB) by E. coli. The harvesting techniques include: cationic potato starch (CPS), cationic corn starch (CCS), aluminum sulfate, and centrifugation. The microalgae-based media were used to grow E. coli to ∼10(13)CFU/mL and produce approximately 7.8% of dry cell weight as PHB. This study demonstrates the feasibility of harvesting wastewater algae to produce PHB and the potential for bioproduct generation.