Bioconversion of R-(+)-limonene to perillic acid by the yeast Yarrowia lipolytica

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.

Cellulolytic potential of a novel strain of Paenibacillus sp. isolated from the armored catfish Parotocinclus maculicauda gut

A cellulolytic bacterial strain, designated P118, isolated from the gut of the tropical fish Parotocinclus maculicauda was identified as belonging to the genus Paenibacillus based on phenotypic and chemotaxonomic characteristics and the 16S rRNA gene sequence. The novel strain was Gram-positive, spore-forming and rod-shaped. Catalase but not oxidase was produced. Carboxymethylcellulose was hydrolyzed but starch or gelatin was not. Acetoin production was negative whereas nitrate reduction and urease production were positive. Many carbohydrates served as carbon sources for growth. MK-7 was the predominant isoprenoid quinone. Anteiso-C15:0 (38.73 percent) and C16:0 (20.85 percent) were the dominant cellular fatty acids. Strain P118 was closely related to Paenibacillus amylolyticus NRRL NRS-290, P. pabuli HSCC 492, P. tundrae Ab10b, P. xylanexedens B22a, and P. tylopili MK2 with 98.3-98.8 percent 16S rRNA gene sequence similarity. The results presented here suggest that strain P118 represents a novel species of the genus Paenibacillus and it is a potential strain for further studies concerning its role in the production of industrially important products from cellulosic biomass.

Chloroperoxidase mediated oxidation of chlorinated phenols using electrogenerated hydrogen peroxide

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 mVSCE, 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 percent, 93 percent and 88 percent 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.

Corn oil favours protease production by Streptomyces viridosporus T7A

Besides of being largely used for antibiotic production, streptomyces have also been pointed out as good producers of enzymes with industrial interest such as protease. In this work, the effect of corn oil on protease production by S. virisdoporus T7A was investigated as part of a wide project for microbial protease production. Culture media contained 0.65(per cent) yeast as nitrogen source, corn oil or corn oil combined with 0.65(per cent) glucose as carbone source, plus mineral salts. In both cases, corn oil used in three differents concentrations, 0.1, 0.5 and 1(per cent) (p/V). All experiments were carried out in agitated flasks at 37§C for 105 hours. Higher protease activty (52 U/L) was obtained in medium containing 0.65(per cent) glucose and 1.0(per cent) corn oil as carbon sources. Protease activity responded positively to the increase in the medium C/N ratio, i.e., to the increment in oil concentration. Our results also suggested that corn oil favours enzyme stability during the fermentation.

Thermal stability of xylanases produced by "Aspergillus awamori"

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 35-55ºC, 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(per cent)) was found for endoxylanase at -4ºC for 165 days. Yet for (beta)-xylosidase, and activity decrease of approximately 20(per cent) was observed during the first 15 days of storage, maintaining roughly 75(per cent) of initial activity until the end of the experiment.