An-Fei Hsu

Immobilized lipase‐catalysed production of alkyl esters of restaurant grease as biodiesel

Simple alkyl ester derivatives of restaurant grease were prepared using immobilized lipases as biocatalysts. The lipases studied included those of Thermomyces lanuginosa and Candida antarctica supported on granulated silica (gran‐T.l. and gran‐C.a., respectively), C. antarctica supported on a macroporous acrylic resin (SP435) and Pseudomonas cepacia immobilized within a phyllosilicate sol‐gel matrix (IM PS‐30). All alcoholysis reactions were carried out in solvent‐free media employing a one‐step addition of the alcohol to the reaction system. Of the lipases studied, IM PS‐30 was found to be the most effective in catalysing the methanolysis and ethanolysis of grease. The processes catalysed by gran‐T.l. and gran‐C.a. lipases gave poor conversions to esters, and the SP435‐catalysed reactions gave intermediate yields of ethyl and methyl esters. Water activity (aw) was an important factor in the methanolysis reactions; reaction media with aw<0.5 resulted in the highest conversions to methyl esters. Molecular sieves also improved methyl ester yields by as much as 20% in transesterification reactions catalysed by IM PS‐30. The immobilized lipases also were evaluated for their ability to produce alkyl esters of grease with several additional normal and branched‐chain alcohols.

Immobilization of Pseudomonas cepacia lipase in a phyllosilicate sol-gel matrix : effectiveness as a biocatalyst

A novel procedure is described for immobilizing a lipase from Pseudomonas cepacia (PS‐30) within a phyllosilicate sol–gel matrix. The method is based on cross‐linking a phyllosilicate clay with silicate polymers produced by the controlled hydrolysis of tetramethyl orthosilicate (TMOS). The activity of the phyllosilicate sol–gel‐immobilized lipase was dependent upon the type of alkylammonium salt, inorganic catalyst and volume ratio of phyllosilicate clay to TMOS used. Lipase PS‐30 immobilized in this way was more stable and had higher activity compared with the free lipase. Studies on the lipase‐catalysed esterification of lauric acid with octan‐1‐ol in iso‐octane showed that under controlled water activity conditions the phyllosilicate sol–gel‐immobilized lipase had better activity compared with other supported lipase preparations. In addition, the phyllosilicate sol–gel‐immobilized lipase was reusable for at least five esterification cycles without significant loss of activity.

Phyllosilicate sol-gel immobilized lipases for the formation of partial acylglycerides**

Lipase PS-30 (pseudomonas cepacia) and Lipase F (Rhizopus oryzae), immobilized within a phyllosilicate sol-gel matrix, catalyzed the esterification of glycerol with short, medium and long-chain fatty acids to produce mono (MAG), di (DAG) and tri (TAG) acylglycerols. The results from the above esterification reactions were compared to reactions using a commercially available immobilized lipase, Lipozyme IM-60. Time course studies showed that free Lipase PS-30 or Lipase F enhanced esterification reactions with the use of silica-supported glycerol. In contrast, immobilized Lipase PS-30-catalyzed reactions occurred at the same conversion rate when using either free or silica-supported glycerol. For immobilized Lipase F and Lipozyme IM-60 reactions, the use of silica-supported glycerol favored the production of DAG and TAG over MAG. All three immobilized lipases could be reused for acylglycerol production.

Effects of divalent cations on nadh‐linked electron transfer in corn root plasma membrane

The effects of calcium (Ca 2+ ), cadmium (Cd 2+ ), and copper (Cu 2+ ) cations on NADH-linked electron transfer in corn root plasma membrane vesicles were investigated. The reduction of both cytochrome c and ferricyanide were slightly stimulated by Ca 2+ but not significantly affected by Cd 2+ . However, Cd 2+ induced a redox-linked increase in light scattering suggesting an increase in the size/volume of the vesicles. The presence of micromolar levels of Cu 2+ decreased the reduction rates of both cytochrome c and ferricyanide. However, in contrast to ferricyanide reduction, Cu inhibition to the cytochrome c reduction was more effective and was less sensitive to ionic strength. Copper inhibition changed the Michaelis-Menten dependence of the ferricyanide reduction but not that of cytochrome c. These results suggest that the reduction of cytochrome c and ferricyanide must occur at different membrane sites