Sugar Ester Synthesis by Thermostable Lipase from <Emphasis Type="Italic">Streptomyces thermocarboxydus</Emphasis> ME168

The extracellular lipase from Streptomyces thermocarboxydus ME168 was purified to 9.5-fold with 20% yield, following concentration by acetone precipitation, ion exchange chromatography (Resource Q) and gel filtration chromatography (Superdex 200), respectively. The purified enzyme had an apparent molecular mass of 21 kDa by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). The N-terminal sequence of the lipase was ASDFDDQILG and was different from most other reported lipase. The enzyme showed maximum activity at 50 °C with the half-life of 180 min at 65 °C. It showed high stability at a broad pH range of 5.5–9.5 and was thermostable at the temperature range of 25–60 °C. The K _m and V _max were 0.28 mM and 1,428 U/mg, respectively, using p-nitrophenyl palmitate as substrate. It was active toward p-nitrophenyl ester with medium to long acyl chain (C₈–C₁₆). Lipase activity was inhibited by Zn²⁺, dithiothreitol (DTT), EDTA and some organic solvents, e.g., ethanol, acetone, dioxane, acetronitrile, tert-butanol and pyridine. Immobilized crude lipase of S. thermocarboxydus ME168 on celite could be used to synthesize sugar esters from glucose and vinyl acetate, vinyl butyrate or vinyl caproate in tert-butanol:pyridine (55:45 v/v) at 45 °C with conversion yields of 93, 67 and 55%, respectively.     

Optimization of Cellulase and Xylanase Productions by Streptomyces thermocoprophilus Strain TC13W Using Oil Palm Empty Fruit Bunch and Tuna Condensate as Substrates

The modified medium composed of the alkaline-pretreated oil palm empty fruit bunch (APEFB) and tuna condensate powder was used for cellulase and xylanase productions by Streptomyces thermocoprophilus strain TC13W. The APEFB contained 74.46% (w/w) cellulose, 15.72% (w/w) hemicellulose, and 6.40% (w/w) lignin. The tuna condensate powder contained 55.49% (w/w) protein and 11.05% (w/w) salt. In the modified medium with only 6.75 g/l tuna condensate powder, 10 g/l APEFB, and 0.5 g/l Tween 80, S. thermocoprophilus strain TC13W produced cellulase 4.9 U/ml and xylanase 9.0 U/ml. The enzyme productions in the modified medium were lower than cellulase (6.0 U/ml) and xylanase (12.0 U/ml) productions in the complex medium (CaCl₂ 0.1, MgSO₄·7H₂O 0.1, KH₂PO₄ 0.5, K₂HPO₄ 1.0, NaCl 0.2, yeast extract 5.0, NH₄NO₃ 1.0, Tween 80 0.5). When tuna condensate powder in the modified medium was reduced to 5.0 g/l and Tween 80 was increased to 1.5 g/l, S. thermocoprophilus strain TC13W produced cellulase and xylanase activities of 9.1 and 12.1 U/ml, respectively. This study shows that the cost of enzyme production could be reduced by using pretreated EFB and tuna condensate as a carbon and a nitrogen source, respectively.