Biodiesel, a non-toxic and biodegradable fuel, has recently become a major source of renewable alternative fuels. Utilization of lipase as a biocatalyst to produce biodiesel has advantages over common alkaline catalysts such as mild reaction conditions, easy product separation, and use of waste cooking oil as raw material. In this study, Pseudomonas cepacia lipase immobilized onto magnetic nanoparticles (MNP) was used for biodiesel production from waste cooking oil. The optimal dosage of lipase-bound MNP was 40% (w/w of oil) and there was little difference between stepwise addition of methanol at 12 h- and 24 h-intervals. Reaction temperature, substrate molar ratio (methanol/oil), and water content (w/w of oil) were optimized using response surface methodology (RSM). The optimal reaction conditions were 44.2 °C, substrate molar ratio of 5.2, and water content of 12.5%. The predicted and experimental molar conversions of fatty acid methyl esters (FAME) were 80% and 79%, respectively.

Carrot pomace, a major agricultural waste from the juice industry, was used as a feedstock for bioethanol production by fermentation with the thermotolerant yeast Kluyveromyces marxianus. Treatment of the carrot pomace with Accellerase^TM 1000 and pectinase at 50 °C for 84 h, resulted in conversion of 42% of its mass to fermentable sugars, mainly glucose, fructose, and sucrose. Simultaneous saccharification and fermentation (SSF) at 42 °C was performed on 10% (w/v) carrot pomace; the concentration of ethanol reached 18 g/L and the yield of ethanol from carrot pomace was 0.18 g/g. The highest ethanol concentration of 37 g/L was observed with an additional charge of 10% supplemented to the original 10% of carrot pomace after 12 h; the corresponding yield was 0.185 g/g. Our results clearly demonstrated the potential of combining a SSF process with thermotolerant yeast for the production of bioethanol using carrot pomace as a feedstock.

Response surface methodology (RSM) was employed to optimize the extracellular lipase production by Burkholderia sp. HL-10. Preliminary tests showed that olive oil, tryptone and Tween-80 exhibited significant effects on the lipase production. The optimum concentrations of these three components were determined using a faced-centered central composite design (FCCCD). The analysis of variance revealed that the established model was significant (p < 0.01). The optimized medium containing 0.65% olive oil (v/v), 2.42% tryptone (w/v) and 0.15% Tween-80 (v/v) resulted in a maximum activity of 122.3 U/mL, about three fold higher than that in basal medium. Approximately 99% of validity of the predicted value was achieved.

(1) Background: Lipids derived from oleaginous microbes have become promising alternative feedstocks for biodiesel. This is mainly because the lipid production rate from microbes is one to two orders of magnitude higher than those of energy crops. However, the conventional process for converting these lipids to biodiesel still requires a large amount of energy and organic solvents; (2) Methods: In this study, an oleaginous yeast, Rhodotorula glutinis, was used for direct transesterification without lipid pre-extraction to produce biodiesel, using sulfuric acid or sodium hydroxide as a catalyst. Such processes decreased the amount of energy and organic solvents required simultaneously; (3) Results: When 1 g of dry R. glutinis biomass was subject to direct transesterification in 20 mL of methanol catalyzed by 0.6 M H₂SO₄ at 70 °C for 20 h, the fatty acid methyl ester (FAME) yield reached 111%. Using the same amount of biomass and methanol loading but catalyzed by 1 g/L NaOH at 70 °C for 10 h, the FAME yield reached 102%. The acid-catalyzed process showed a superior moisture tolerance; when the biomass contained 70% moisture, the FAME yield was 43% as opposed to 34% of the base-catalyzed counterpart; (4) Conclusions: Compared to conventional transesterification, which requires lipid pre-extraction, direct transesterification not only simplifies the process and shortens the reaction time, but also improves the FAME yield.

We entrapped lipase from Pseudomonas cepacia in polyallylamine-mediated biomimetic silica, and then applied entrapped lipase to the synthesis of biodiesel with soybean oil or waste cooking oil as a feedstock. The effects of reaction temperature, substrate molar ratio (methanol/oil) and n-hexane content (w/w of oil) were evaluated using response surface methodology (RSM) combined with Box-Behnken design. The optimal reaction conditions for soybean oil were 43.6 °C, substrate molar ratio of 4.3%, and 75% n-hexane. The predicted and experimental values of biodiesel conversion were 79% and 76%, respectively. The optimal reaction conditions for waste cooking oil were 43.3 °C, substrate molar ratio of 5%, and 38% n-hexane. The predicted and experimental values of conversion were 68% and 67%, respectively. The conversion efficiency remained the same even after 1-month storage of entrapped lipase at 4 °C or room temperature.