| Increased level of CO2in the atmosphere causing global warming, and limitation ofnon-renewable fossil fuel reserves are two critical issues in the world today. In recent years,clean and renewable energy has been developing rapidly. Algal biofuel is regarded as one ofthe best solutions to curb with these issues in the short and long run. However, costs fordewatering of biomass and extraction of lipids have limited commercial scale production ofbiofuel from algal biomass. The focus of this study is on the rapid method for determinationof lipid from algae and sustainable production of purified oil from the algal speciesNannochloris sp.. This procedure consists of three steps:(i) dewatering algal sludge from85-95%to30-40%water content with ethanol (83%V/V),(ii) obtaining a crude lipid extractsby microwave-assisted extraction from the wet biomass with ethanol (95%V/V) and (iii)purification of this crude lipid extracts by extraction of the oil with hexane. The detailedcontents are as shown below:(1) In this chapter, the difference of four methods (Bligh-Dyer, modified Bligh-Dyer,ASTM standard and direct saponification methods) was systematically compared ondetermination of total lipid content in three microalgae (Nannochloris sp., Chlorella vulgarisand Pavlova viridis). The results showed that the modified Bligh-Dyer had steady extractionoutcomes with the highest transesterifiable lipids recoveries at93.7%,85.0%and88.6%inthree microalgae, respectively. Moreover, the modified Bligh-Dyer method was proved to bea rapid and easy manipulated method with few sample size (0.25g) and short time (60.0min)for determination of lipid from algae, which could be an alternative of ASTM standardmethod in laboratories.(2) In this present investigation, extraction of water from the algal sludge with an ethanolsolution as an alternative to conventional drying was carried out in marine Nannochloropsissp.. The optimal ethanol concentration, ratio of ethanol solution to water in algal sludge anddewatering times were83%(V/V),1:1and1, respectively. Under the optimized conditions,the water content of wet biomass was decreased from89.1%to37.4%with transesterifiablelipids of algae loss rate of6.0%. The dewatered biomass could be good raw material for thewet lipid extraction procedure. (3) Ethanol (95%V/V) was used to extract lipids from the wet biomass of the microalgaeNannochloropsis sp. with five different pre-treatment methods (autoclave, ultra sonication,microwave, bead-beater and deep freezing). Optimization of extraction parameters wereperformed and highest transesterifiable lipids yield (13.4%(w/w)) was obtained at90.0℃temperature,80.0min time and solvent-to-solid ratio as20:1with microwave pre-treatment.GC-MS analysis indicated that crude oil containing high percentages of C16:0(32.3%), C18:0(19.1%) and C18:1(21.1%), which was suitable for the biodiesel production. Besides,30-40wt%water content showed no significant impact upon extraction yield, which could be theobject region of dewatering processing of algal sludge.(4) A simple and suitable industrial-scale purification procedure was developed that wascapable of recovering98.5%of transesterifiable lipids from crude alcoholic extracts viaforming biphasic system by adding water, CaCl2and hexane. The optimum conditions wereestimated as follows:(i) water content of50.0%(V/V) in the hydroalcoholic solution,(ii)CaCl2dosage0.1mol/L,(iii) hexane/hydroalcoholic phase ratio of0.4(vol/vol) and (iv)720.00min stock-still time. Further-more, the processing was capable of removing79.7%,67.9%,69.7%and98.8%of chlorophyll a, chlorophyll b, carotenoids and proteincontamination of the crude extracts, respectively. In addition, the fatty acid composition oflipids had no significant change during purification procedure. |
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