Production of chiral epoxides: Epoxide hydrolase-catalyzed enantioselective hydrolysis

Chiral epoxides are highly valuable intermediates, used for the synthesis of pharmaceutical drugs and agrochemicals. They have broad scope of market demand because of their applications. A major challenge in modern organic chemistry is to generate such compounds in high yields, with high stereo- and regio-selectivities. Epoxide hydrolases (EH) are promising biocatalysts for the preparation of chiral epoxides and vicinal diols. They exhibit high enantioselectivity for their substrates, and can be effectively used in the resolution of racemic epoxides through enantioselective hydrolysis. The selective hydrolysis of a racemic epoxide can produce both the corresponding diols and the unreacted epoxides and vicinal diol has prompted researchers to explore their use in the synthesis of epoxides and diols with high ee values.     

Production and characteristics of a bioflocculant produced by Bacillus sp. F19

A bioflocculant-producing bacterium isolated from soil was identified as Bacillus sp. and the bioflocculant produced was named MBFF19. Effects of physico-chemical conditions including pH, carbon sources and nitrogen sources on MBFF19 production were studied. Chemical analyses of the purified bioflocculant MBFF19 indicated that it was a sugar-protein derivative, composed of neutral sugar (3.6%, w/w), uronic acid (37.0%, w/w), amino sugars (0.5%, w/w) and protein (16.4%, w/w). The two neutral sugar components were mannose and glucose and the molar ratio was 1.2:1. Infrared spectrophotometry analysis revealed that MBFF19 contained carboxyl, hydroxyl and methoxyl groups in its structural. Flocculating properties of bioflocculant MBFF19 was examined using kaolin, activated carbon and fly coal suspension. Cation supplement had no positive effects on the flocculating activity whereas the presence of Fe3+ inhibited flocculation. Influences of pH and bioflocculant dosage on the flocculation were also examined.     

Production of a cellulase-free xylanase from agricultural waste materials by a thermotolerant Streptomyces sp.

1444 microorganisms were isolated from soil samples from the northern Thai and screened at 55 °C by using basal medium supplemented with 1% carboxymethyl cellulose as a sole carbon source. One isolate, Streptomyces Ab106, had a high activity of a cellulase-free xylanase also without mannanase activity. The maximum cellulase-free xylanase activities of 3.5, 3.3, 3.1 and 2.7 IU were after growth of the organism with 1% (w/v) corn hull, corncob, bagasse and oat spelt xylan, respectively, at 55 °C for 6 days, respectively. The activity was more than 5 times higher than that at 35 °C.     

Four novel yeasts from decaying organic matter: Blastobotrys robertii sp. nov., Candida cretensis sp. nov., Candida scorzettiae sp. nov. and Candida vadensis sp. nov

Four novel yeast species are described, two from decaying mushrooms, viz. Candida cretensis and Candida vadensis, and two from rotten wood, viz. Blastobotrys robertii and Candida scorzettiae. Accession numbers for the CBS and ARS Culture Collections, and GenBank accession numbers for the D1/D2 domains of the large subunit of ribosomal DNA are: B. robertii CBS 10106^T, NRRL Y-27775, DQ839395; C. cretensis CBS 9453^T, NRRL Y-27777, AY4998861 and DQ839393; C. scorzettiae CBS 10107^T, NRRL Y-27665, DQ839394; C. vadensis CBS 9454^T, NRRL Y-27778, AY498863 and DQ839396. The GenBank accession number for the ITS region of C. cretensis is AY498862 and that for C. vadensis is AY498864. C. cretensis was the only species of the four that displayed fermentative activity. All four type strains grew on n-hexadecane. C. scorzettiae is the only one of the new species that assimilates some phenolic compounds, viz. 3-hydroxy derivatives of benzoic, phenylacetic and cinnamic acids, but not the corresponding 4-hydroxy acids. This is indicative of an operative gentisate pathway.     

Overproduction of an extracellular polysaccharide possessing high lipid emulsion stabilizing effects by Bacillus sp.

Bacillus sp. CP912, producing an extracellular biopolymer, was isolated from the soil. Maximum accumulation of the biopolymer was 10 g l^–1 culture broth with a yield of 88% from glucose consumed. The biopolymer was purified with several precipitation steps using ethanol and cetyl-trimethyl-ammonium bromide. Carbohydrate analyses using various color reactions, infrared spectroscopy, and high performance liquid chromatography revealed that the biopolymer is a homopolysaccharide. The lipid emulsifying capacity of the polysaccharide was 100%, while that of xanthan gum was 94%.     

Candida alocasiicola sp. nov., Candida hainanensis sp. nov., Candida heveicola sp. nov. and Candida musiphila sp. nov., novel anamorphic, ascomycetous yeast species isolated from plants

In a taxonomic study on the ascomycetous yeasts isolated from plant materials collected in tropical forests in Yunnan and Hainan Provinces, southern China, four strains isolated from tree sap (YJ2E(T)) and flowers (YF9E(T), YWZH3C(T) and YYF2A(T)) were revealed to represent four undescribed yeast species. Molecular phylogenetic analysis based on the large subunit (26S) rRNA gene D1/D2 domain sequences showed that strain YJ2E(T) was located in a clade together with Candida haemulonii and C. pseudohaemulonii. Strain YF9E(T) was most closely related to C. azyma and strain YWZH3C(T) to C. sorbophila and C. spandovensis. Strain YYF2A(T) was clustered in a clade containing small-spored Metschnikowia species and related anamorphic Candida species. The new strains differed from their closely related described species by more than 10% mismatches in the D1/D2 domain. No sexual states were observed for the four strains on various sporulation media. The new species are therefore assigned to the genus Candida and described as Candida alocasiicola sp. nov. (type strain, YF9E(T) = AS 2.3484(T) = CBS 10702(T)), Candida hainanensis sp. nov. (type strain, YYF2A(T) = AS 2.3478(T) = CBS 10696(T)), Candida heveicola sp. nov. (type strain, YJ2E(T) = AS 2.3483(T) = CBS 10701(T)) and Candida musiphila sp. nov. (type strain, YWZH3C(T) = AS 2.3479(T) = CBS 10697(T)).     

Microbial corrosion monitoring by an amperometric microbial biosensor developed using whole cell of Pseudomonas sp.

A microbial biosensor was developed for monitoring microbiologically influenced corrosion (MIC) of metallic materials in industrial systems. The Pseudomonas sp. isolated from corroded metal surface was immobilized on acetylcellulose membrane and its respiratory activity was estimated by measuring oxygen consumption. The microbial biosensor was used for the measurement of sulfuric acid in a batch culture medium contaminated by microorganisms. A linear relationship between the microbial sensor response and the concentration of sulfuric acid was observed. The response time of biosensor was 5 min and was dependent on the immobilized cell loading of Pseudomonas sp., pH, temperature and corrosive environments. The microbial biosensor response was stable, reproducible and specific for sensing of sulfur oxidizing bacterial activity.     

Microbial Metabolism of Quinoline by Comamonas sp.

An aerobic bacterial strain which can use quinoline as the sole carbon and energy source has been isolated from activated sludge and identified as Comamonas sp. The microbial metabolism of quinoline by this strain has been investigated. A pH 8 and a temperature of 30 °C were the optimum degradation conditions of quinoline. Five intermediates including 2-oxo-1,2-dihydroquinoline, 5-hydroxy-6-(2-carboxyethenyl)-1H-2-pyridone, 6-hydroxy-2-oxo-1,2-dihydroquinoline, 5,6-dihydroxy-2-oxo-1,2-dihydroquinoline, and 8-hydroxy-2-oxo-1,2-dihydroquinoline were found during quinoline biodegradation. The presence of these intermediates suggested that at least two pathways were involved for quinoline degradation by Comamonas sp. and a reasonable degradation route was proposed to account for the intermediates observed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Pullulanases of alkaline and broad pH range from a newly isolated alkalophilicBacillus sp. S-1 and aMicrococcus sp. Y-1

Summary Two highly alkalophilic bacteria, and potent producers of alkaline pullulanase, were isolated from Korean soils. The two isolates, identified asBacillus sp. S-1 andMicrococcus sp. Y-1, grow on starch under alkaline conditions and effectively secrete extracellular pullulanases. The two isolates were extremely alkalophilic since bacterial growth and enzyme production occurred at pH values ranging from pH 6.0 to 12.0 forMicrococcus sp. Y-1 and pH 6.0 to 10.0 forBacillus sp. S-1. Both strains secrete enzymes that possess amylolytic and pullulanolytic acitivities. Extracellular crude enzymes of both isolates gave maltotriose as the major product formed from soluble starch and pullulan hydrolysis. Compared to other alkalophilic microbes such asMicrococcus sp. (0.57 units ml^–1),Bacillus sp. KSM-1876 (0.56 units ml^–1) andBacillus No. 202-1 (1.89 units ml^–1) these isolates secreted extremely high concentrations (7.0 units ml^–1 forBacillus sp. S-1 and 7.6 units ml^–1 forMicrococcus sp. Y-1) of pullulanases in batch culture. The pullulanase activities from both strains were mostly found in the culture medium (85–90%). The extracellular enzymes of both bacteria were alkalophilic and moderately thermoactive; optimal activity was detected at pH 8.0–10.0 and between 50 and 60°C. Even at pH 12.0, 65% of original Y-1 pullulanase activity and 10% of S-1 pullulanase activity remained. The two newly isolated strains had broad pH ranges and moderate thermostability for their enzyme activities. These result strongly indicate that these new bacterial isolates have potential as producers of pullulanases for use in the starch industry.     

Biodegradation of 1,4-dioxane and transformation of related cyclic compounds by a newly isolated Mycobacterium sp. PH-06

A new bacterial strain PH-06 was isolated using enrichment culture technique from river sediment contaminated with 1,4-dioxane, and identified as belonging to the genus Mycobacterium based on 16S rRNA sequencing (Accession No. EU239889). The isolated strain effectively utilized 1,4-dioxane as a sole carbon and energy source and was able to degrade 900 mg/l 1,4-dioxane in minimal salts medium within 15 days. The key degradation products identified were 1,4-dioxane-2-ol and ethylene glycol, produced by monooxygenation. Degradation of 1,4-dioxane and concomitant formation of metabolites were demonstrated by GC/MS analysis using deuterium labeled 1,4-dioxane (1,4-dioxane-d8). In addition to 1,4-dioxane, this bacterium could also transform structural analogues such as 1,3-dioxane, cyclohexane and tetrahydrofuran when pre-grown with 1,4-dioxane as the sole growth substrate. Our results suggest that PH-06 can maintain sustained growth on 1,4-dioxane without any other carbon sources.     

Secondary carotenoids formation by the green alga Chlorococcum sp.

The effects of temperature, pH and oxygen level onsecondary carotenoids (SC) accumulation in Chlorococcum sp. were investigated. The optimaltemperature, pH and oxygen level for the yields ofsecondary carotenoids and astaxanthin were35 ^°C, pH 8 and 10% (v/v), respectively. Whilethe ratio (R) of products containing hydroxyl group(s) to those containing keto group (s) increased withthe increase of temperature and pH, R value decreasedwith the level of oxygen. These results indicate thathigher temperature and pH favor the introduction ofhydroxyl group to the corresponding substrates,however, under high oxygen level keto group wasrelatively easy to be added compared to the additionof hydroxyl.     

Production of cholesterol oxidase by a newly isolated Rhodococcus sp.

Fifteen strains of microorganisms with ability to degrade cholesterol were isolated. Among them a Gram-positive, non-motile, non-sporing bacterium with meso-DAP in the cell wall and with a rod-coccus cycle showed the highest ability for cholesterol degradation. It was identified as Rhodococcus sp. strain 2C and was deposited by code 1633 in Persian type culture collection (PTCC). This strain was able to produce high levels of both extracellular and cell-bound cholesterol oxidases in media containing cholesterol as a sole carbon source. The effects of medium composition and physical parameters on cholesterol oxidase production were studied. The optimized medium was found to contain cholesterol 0.15% (w/v), yeast extract 0.3% (w/v), diammonium hydrogen phosphate 0.1% (w/v), Tween 80 (0.05%). The optimum pH and temperature for cholesterol oxidase production in optimized medium were found to be 8–30 °C respectively. Triton X-100 showed the greatest effect in releasing the cell-bound enzyme. The first and most probably the main metabolite of cholesterol degradation was purified and identified as 4-cholestene-3-one.     

Expandase-like activity mediated cell-free conversion of ampicillin to cephalexin by Streptomyces sp. DRS I

Cell-free extracts of Streptomyces sp. DRS I converted ampicillin to cephalexin, presumably due to the activity of the enzyme, expandase. The extract was fractionated and characterized by colorimetric and chromatographic measurements coupled with disc-agar diffusion bioassay against an ampicillin-resistant, cephalexin-sensitive E. coli strain. Though expandase could not be identified, the presence of a hitherto unreported expandase in Streptomyces sp. DRS I is suggested.     

Infection of Glaucocystis nostochinearum (Glaucophyta) by Lagenidium sp. (Oomycota) and its hyperparasite Pythiella sp. (Oomycota)

The glaucophyte Glaucocystis nostochinearum has to our knowledge been observed to be infected by a parasite for the first time. It was found in samples taken from the northernmost freshwater pond in Germany (on the island of Sylt). The fungal parasite was identified as the oomycete Lagenidium sp. which itself was parasitised by another oomycete, Pythiella sp.     

Investigation of lipase production by a new isolate of Aspergillus sp.

Fungi isolated from soil were screened for exogenous lipolytic activity. The highest lipase activity was found in a new soil isolate of Aspergillus sp. Some optimal cultural parameters influencing the growth and production of extracellular lipase from this Aspergillus sp. were investigated. The lipase yield was maximum on day 4 of incubation of the culture at pH 5.5 and 30 °C. When the medium was prepared using olive oil as carbon source and peptone as a nitrogen source, better lipase yields were obtained. Aeration enhanced growth and lipase production.     

Transesterification of divinyladipate with glucose at various temperatures by an alkaline protease of Streptomyces sp.

The transesterification of 1 M divinyladipate with 0.25 M glucose in dimethylformamide (DMF) catalyzed by 5 mg ml^–1 alkaline protease (24 units mg^–1 min^–1) from Streptomyces sp. gave 6-O-vinyladipoyl d-glucose as the main product with yields are between 60 and 90%. The optimum temperature for the reaction was about 50 °C.     

The role of kairomones in prey finding by Diomus sp. and Exochomus sp., two coccinellid predators of the cassava mealybug, Phenacoccus manihoti

We studied searching behaviour of Diomus sp., a coccinellid predator introduced into Africa as a natural enemy of the cassava mealybug, when searching on cassava leaves, and compared its behaviour with the searching behaviour of Exochomus sp., an African predator of mealybugs (MB's). Female adults of Diomus and Exochomus spent more time searching on cassava leaves previously infested with cassava MB than on clean cassava leaves, in response to substances produced by MB's (wax and/or honeydew) still present on these leaves as kairomones after removal of the MB's. Both species were also arrested by wax and/or honeydew of the citrus mealybug, Planococcus citri. When offered a choice between kairomones of both MB species only experienced Diomus (reared on cassava MB) showed a clear preference for kairomone of cassava MB. Separate influences of wax and honeydew were tested. Wax from cassava MB was an arrestment stimulus for both coccinellid species. Honeydew produced by cassava MB arrested Exochomus and inexperienced Diomus.

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Zusammenfassung Das Suchverhalten auf Cassaveblätter des coccinelliden Raübers Diomus, eines aus Süd Amerika importierten natürlichen Feindes der Cassaveschmierlaus wurde studiert und verglichen mit dem Suchverhalten eines afrikanischen Räubers von Schmierläusen, Exochomus sp.. Weiblichen Adulten von Diomus un Exochomus verwendeten mehr Zeit auf Cassaveblätter wenn diese Blätter vorher mit Cassaveschmierläuse infiziert waren als auf uninfizierte Blätter, und gebrauchten Substanzen (Wachs und/oder Honigtau) die von Schmierläuse produziert wurden und nach der Entfernung der Schmierläuse auf die Blätter zugeblieben waren als Kairomonen.Beide Arten wurden auch von Wachs und/oder Honigtau der Citrusschmierlaus, Planococcus citri, auf den Blätter arretiert. Wenn die Tiere wahlen könnten zwischen Kairomone der beiden Schmierlausarten wurden die Kairomonen der Cassaveschmierlaus nur von erfahrenen Diomus-Individuen, die auf Cassaveschmierlaüse aufgezogen wurden, bevorzugt.Die Einflüsse von Wachs und Honigtau wurden separat geprüft. Wachs von Exuvien der Cassaveschmierlaus ist ein Arretierungsstimulus für beide Räuberarten. Von Cassaveschmierläusen produzierten Honigtau arretierte Exochomus-und unerfahrene Diomus-Individuen.

     

Biodegradation of Cypermethrin by <Emphasis Type="Italic">Micrococcus</Emphasis> sp. strain CPN 1

A bacterium capable of utilizing pyrethroid pesticide cypermethrin as sole source of carbon was isolated from soil and identified as a Micrococcus sp. The organism also utilized fenvalerate, deltamethrin, perimethrin, 3-phenoxybenzoate, phenol, protocatechuate and catechol as growth substrates. The organism degraded cypermethrin by hydrolysis of ester linkage to yield 3-phenoxybenzoate, leading to loss of its insecticidal activity. 3-Phenoxybenzoate was further metabolized by diphenyl ether cleavage to yield protocatechuate and phenol as evidenced by isolation and identification of metabolites and enzyme activities in the cell-free extracts. Protocatechuate and phenol were oxidized by ortho-cleavage pathway. Thus, the organism was versatile in detoxification and complete mineralization of pyrethroid cypermethrin     

Simultaneous production of hydrogen and bioflocculant by Enterobacter sp. BY-29

Hydrogen and a bioflocculant could be produced simultaneously by anaerobic culture of Enterobacter sp. BY-29. For production of hydrogen and the bioflocculant by cell culture of the bacterium in batch cultures, cultivation at 37 °C in a medium containing glucose as a carbon source and Polypepton as a nitrogen source was found to be suitable. In continuous production of hydrogen and the bioflocculant by cell culture or immobilized cells of the bacterium, the hydrogen production rate and hydrogen yield by the immobilized cells on porous glass beads in stirred and column reactors were higher than those by the cell culture in a stirred reactor. However, production of the bioflocculant by the cell culture was superior to that by the immobilized cells in continuous production.     

Classification of novel soil streptomycetes as Streptomyces aureus sp. nov., Streptomyces laceyi sp. nov. and Streptomyces sanglieri sp. nov

The taxonomic positions of soil isolates known as Streptomyces groups A, B and C were clarified. Comparative 16S rDNA sequence studies indicated that representatives of all three taxa formed distinct phyletic lines within the Streptomyces tree though the group A strains were shown to be related to Streptomyces griseus and associated validly described species. The taxonomic integrity of all three groups was highlighted by DNA:DNA relatedness and ribotype data though the group A strains encompassed a higher degree of genetic variation than the group B and C strains. In light of these and earlier phenotypic data it is proposed that Streptomyces groups A, B and C be given species status as Streptomyces sanglieri sp. nov., Streptomyces aureus sp. nov. and Streptomyces laceyi sp. nov., respectively. This revised version was published online in June 2006 with corrections to the Cover Date.