Study On The Stability Of The Alkaline Lipase From Penicillium Expansum

Stable enzymes are generally not susceptible to deactivation fungal lipase stability is even worse. Improve enzyme stability at home and abroad, including two areas : 1. Changes to improve environmental conditions around the enzyme molecule enzyme molecules stability. 2. From the level of molecules to transform the structure of enzyme molecules. This kind of study in accordance with paragraph 1 of the extension of pro-line mycophenolate lipase stability of the study, results are summarized as follows :1. Fermentation medium containing 5% of soybean meal, 1.2% of corn starch may help enzymes stability; 0.03% of K₂SO₄ and 0.03% of FeSO₄ were conducive to both the synthesis and the stability of lipase. Addition of permeable agent to the fermentation medium was harmful to both the growth and metabolic of the species, and it would be unfavorable to the stability of lipase.2. The optimum pH to maintain the lipase activity in the fermentation broth and filtration within 20 hours was 8.5. and pH 6.0 for the lipase activity in the mycelium; the lipase stability was decreased with the increasing of the temperature and storage time.3. A protease was synthesized and reached peak in 20 hours during the growth of Penicillium expansum FS1884. Whereas the lipase was synthesized in 20 to 40 hr, hence the protease have little effect on the synthesis of lipase. However, even a small amount of protease in the late of fermentation may lead to partial hydrolyzing of lipase. The study showed that the protease activity was inhibited by addition of EDTA, and the lipase activity can be enhanced by EDTA. The molecule weight of the protease was assayed as 52.5 kDa after purification of the protein, which provided a reference for selection of suitable molecule screen.4. The stability of lipase was declined after addition of equate amount of the starch and fiber separated from the crude enzyme; the lipase activity had little changed after addition equate amount of total sugar and metal ions (in the style of metal compounds) isolated from the crude enzyme.5. The half life of the crude lipase thermal stability was increased by adding a certain concentration of KCI, CaCl₂, sodium tetraborate, sodium succinic acid, sorbitol, glycerol to the crude enzyme and incubating at temperatures of 35℃, 25℃, 15℃for 2, 4 and 9 days, respectively. Results of orthogonal test showed that the optimum stable agent for liquid lipase was composted of 4 mM Ca²⁺, 0.0313 M of sodium tetraborate and 4 M of glycerol, which would increase the half life of lipase thermal stability for 84 hrs at a temperature of 40℃, and 790 hrs at 37℃. The optimum stable agent for solid lipase was made of 2 mM of Ca²⁺, 0.0313 M of sodium tetraborate and 0.5% of sorbitol, which would enhance the half life of lipase thermal stability for 30 hrs at a temperature of 40℃, and 166 hr at 35℃.