Perillyl derivatives are increasingly important due to their flavouring and antimicrobial properties as well as their potential as anticancer agents. These terpenoid species, which are present in limited amounts in plants, may be obtained via bioconversion of selected monoterpene hydrocarbons. In this study, seventeen yeast strains were screened for their ability to oxidize the exocyclic methyl group in the p-menthene moiety of limonene into perillic acid. Of the yeast tested, the highest efficiency was observed for Yarrowia lipolytica ATCC 18942. The conversion of R (+)-limonene by Y. lipolytica was evaluated by varying the pH (3 to 8) and the temperature (25 to 30 ºC) in a reaction medium containing 0.5% v/v limonene and 10 gµL of stationary phase cells (dry weight). The best results, corresponding to 564 mgµL of perillic acid, were obtained in buffered medium at pH 7.1 that was incubated at 25 ºC for 48 h. The stepwise addition of limonene increased the perillic acid concentration by over 50%, reaching 855 mgµL, whereas the addition of glucose or surfactant to the reaction medium did not improve the bioconversion process. The use of Y. lipolytica showed promise for ease of further downstream processing, as perillic acid was the sole oxidised product of the bioconversion reaction. Moreover, bioprocesses using safe and easy to cultivate yeast cells have been favoured in industry.

Chloroperoxidase (CPO) from Caldariomyces fumago catalyses the oxidation of several chlorinated phenols (CP) commonly found in industrial waste waters in the presence of hydrogen peroxide. This study compares the direct addition of hydrogen peroxide (DA) with its continuous electrogeneration (EG) during the enzymatic oxidation of CP. Reaction mixtures were studied containing chemically modified CPO, hydrogen peroxide and the phenolic substrates: phenol (P), 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and pentachlorophenol (PCP), in 100 mM sodium-potassium phosphate buffer pH 6.0, at 25ºC. Results were compared in terms of residual phenol concentration (oxidation efficiency), precipitate formation (removal) and residual enzyme activity (stability). With the electrochemical system evaluated at -620 mV SCE, and continuous aeration the maximum H2O2 concentration of 1.2 mM was obtained. Under this conditions and after 4 hrs using EG, no phenol or 4-CP were detected, and 97%, 93% and 88% of 2,4-DCP, 2,4,6-TCP and PCP were degraded, respectively. The use of EG improves enzyme half-life time in comparison to the results obtained by DA

The effect of temperature on the activity and stability of endoxylanase and beta-xylosidase from Aspergillus awamori was investigated. The growth of A. awamori in milled sugar cane bagasse produced predominantly extracellular endoxylanase (30 U/ml) and lower amounts of beta-xylosidase (1.3 U/ml). Grown in sugar cane bagasse as the principal carbon source, the microorganism produced a quite stable beta-xylosidase in a temperature range of 35-55°C, but it exhibited a lower thermostable endoxylanase. The thermostability of endoxylanase was enhanced through addition of polyhydric alcohols, mainly 2 M xylitol and sorbitol solutions. Particular stability upon storage (100%) was found for endoxylanase at -4°C for 165 days. Yet for beta-xylosidase, an activity decrease of approximately 20% was observed during the first 15 days of storage, maintaining roughly 75% of initial activity until the end of the experiment.

O presente trabalho trata do estudo do efeito da temperatura na atividade e estabilidade de endo-xilanase e beta-xilosidase produzidas, extracelularmente, por Aspergillus awamori. O cultivo deste microrganismo, em bagaço de cana finamente dividido, produziu predominantemente endo-xilanases (30 U/ml) e menores atividades de beta-xilosidase (1,3 U/ml); esta última exibiu considerável estabilidade em faixa de temperatura variando de 35 a 55°C, por outro lado verificou-se uma menor termo estabilidade para a endoenzima. A estabilidade térmica de endo-xilanase foi aumentada consideravelmente através da adição de polióis, principalmente xilitol e sorbitol em concentração de 2,0 M. No que concerne à estocagem a baixa temperatura (-4°C), observou-se uma estabilidade particular na atividade endo-xilanásica (100%), durante 165 dias, porém, um decréscimo de aproximadamente 20% na atividade beta-xilosidásica foi verificado após os primeiros 15 dias de armazenamento nas mesmas condições, mantendo-se aproximadamente em 75% da atividade inicial no mesmo período de tempo.