Enhancing immobilization of Aspergillus oryzae ST11 lipase on polyacrylonitrile nanofibrous membrane by bovine serum albumin and its application for biodiesel production.

The partially purified lipase from Aspergillus oryzae ST11 was immobilized on the surface-modified electrospun polyacrylonitrile (PAN) nanofibrous membrane. The effects of time and concentrations of glutaraldehyde and bovine serum albumin (BSA) were studied. The immobilized lipase reached the maximum activity at 180 min with the recovered activity of 44.2% (0.22 U/mg-support) in the absence of BSA. After adding 6 mg/mL BSA and 40 mM glutaraldehyde gave the recovered activity at 86.9% (0.43 U/mg-support). It showed the highest stability at pH 7.5 but the soluble lipase was at pH 7.0. In addition, the immobilized lipase was more stable at pH 4.0 and 9.0. The immobilized lipase preserved 56% activity at 70 °C but the soluble lipase had 34% activity. It conserved 86% activity while the soluble lipase had 18% activity after 13 days of storage at 4 °C. The operating parameters such as biocatalyst concentration, water content, and the molar ratio of methanol and palm oil were optimized for biodiesel production. The highest biodiesel conversion (95%) was obtained with the immobilized lipase 15% (w/w), 40% (w/w) 50 mM Tris-HCl buffer pH 7.0 and methanol/palm oil (3.5:1.0). This immobilized lipase could be reused with 82.9% conversion after 10 cycles of batch production.

Magnetic Cross-Linked Enzyme Aggregates of Aspergillus oryzae ST11 Lipase Using Polyacrylonitrile Coated Magnetic Nanoparticles for Biodiesel Production.

The biodiesel production by enzymatic catalysis is the environmentally friendly production process. In this work, the polyacrylonitrile coated magnetic nanoparticles were prepared and used as a core supporter for producing magnetic cross-linked enzyme aggregates (mCLEAs) from Aspergillus oryzae ST11 lipase with the co-feeding of bovine serum albumin (BSA). The highest immobilized lipase activity was 0.09 U/mg-support or 81.7% of recovered activity. The resulting mCLEAs exhibited the desired characteristics; it had improved the stabilities for pH, temperature, as well as storage comparing to free enzyme. Moreover, when this biocatalyst was used for biodiesel production at the optimal conditions (30% w/w of mCLEAs, 30% w/w of water content and stepwise addition of methanol), the biodiesel conversion was 95% within 24 h of reaction, while one-step addition of methanol produced 81% conversion. The mCLEAs could be reused for 5 cycles and retained the biodiesel conversion higher than 60%.

Dodecenyl succinylated alginate as a novel material for encapsulation and hyperactivation of lipases.

Alginate was modified with dodecenyl succinic anhydride (SAC12) in an aqueous reaction medium at neutral pH. The highest degree of succinylation (33.9±3.5%) was obtained after 4h at 30°C, using four mole SAC12 per mol alginate monomer. Alginate was modified with succinic anhydride (SAC0) for comparison, and the structures and thermal properties of alg-SAC0 and alg-SAC12 were evaluated using FTIR, (1)H NMR, and DSC. Calcium-hydrogel beads were formed from native and modified alginates, in which lipases were encapsulated with a load of averagely 76µg lipase per mg alginate, irrespective of the type of alginate. Lipases with a "lid", which usually are dependent on interfacial activation, showed a 3-fold increase in specific activity toward water-soluble substrates when encapsulated in alg-SAC12, compared to the free lipase. Such hyperactivation was not observed for lipases independent of interfacial activation, or for lipases encapsulated in native alginate or alg-SAC0 hydrogels.