Study Of Biodiesel Production By Immobilized Whole Cell Method

The depletion of traditional fossil energy such as petroleum and the increasingly serious environmental pollution problems resulting from it, make human beings begin to look for clean alternative energy with sustainable use, and biodiesel as an environmentally-friendly renewable clean energy gains more and more attention. Biodiesel refers to fatty acid methyl ester or fatty acid ethyl ester produced through the transesterification of vegetable oil and animal fat and short chain alcohol including methanol or ethanol. The existing chemical synthesis used currently possesses some disadvantages such as high energy consumption, deep-colored biodiesel end product and polluting environment, while biodiesel by lipase catalysis method shares some advantages such as mild condition, small alcohol dosage, easy-collecting product and no pollutant emissions when it is used for fuel. Therefore, it has the ability to deal with existing problems caused by chemical methods and is an important development direction in biodiesel industry.In this study, 10 lipase-producing strains were screened and one strain Y₁ among them, with the peak lipase activity, was catalyzed for production of biodiesel. At the same time, related work was conducted as follows.1. Optimal culture conditions for Strain Y₁ were determined. The best fermentation medium for Strain Y₁ contained (g/L): sucrose 5, peptone 15, (NH₄)₂SO₄ 1, K2HPO4 1.5, MgSO₄·7H₂O₂, olive oil 15, Tween 80 (used as inducer). Based on the optimal fermentation medium, the strain was cultured at 30℃, 170 r·min^-1 in rotary shaker for 36h and the maximum enzyme activity reached 73.3U/ml, 4.88 times than the original strain.2. Tolerance of methanol on Strain Y₁ was acclimatized and 4% methanol is favorable for enzyme production. 3. Strain Y₁ whole-cell immobilization: the precipitate of fermentation broth of Strain Y₁ was freeze-dried and immobilization was carried out by utilizing the polyurethane foam method.4.Immobilized whole cells for biodiesel production: transesterification system was constituted: olive oil 9.65g + methanol 3.5 g (methanol was poured into olive oil for three times ,namely, first 1.0g, then added 1.5g in 24h, finally added 1.0g after 48h) + organic solvent (hexane)1.5 g + enzyme 1.2 g. Transesterification products were analyzed by TLC.In this experiment, enzyme production conditions for Strain Y₁ were optimized and tolerance of methanol was acclimatized. In the meantime, immobilized whole cells were investigated and fatty acid methyl esters were successfully synthesized through lipase catalytic transesterification reaction.