Isolation and screening of chromium resistant bacteria from industrial waste for bioremediation purposes / Isolamento e triagem de bactérias resistentes ao cromo de resíduos industriais para fins de biorremediação

Chromium (VI) a highly toxic metal, a major constituent of industrial waste. It is continuously release in soil and water, causes environmental and health related issues, which is increasing public concern in developing countries like Pakistan. The basic aim of this study was isolation and screening of chromium resistant bacteria from industrial waste collected from Korangi and Lyari, Karachi (24˚52ʹ46.0ʺN 66˚59ʹ25.7ʺE and 24˚48ʹ37.5ʺN 67˚06ʹ52.6ʺE). Among total of 53 isolated strains, seven bacterial strains were selected through selective enrichment and identified on the basis of morphological and biochemical characteristics. These strains were designated as S11, S13, S17, S18, S30, S35 and S48, resistance was determined against varying concentrations of chromium (100-1500 mg/l). Two bacterial strains S35 and S48 showed maximum resistance to chromium (1600 mg/l). Bacterial strains S35 and S48 were identified through 16S rRNA sequence and showed 99% similarity to Bacillus paranthracis and Bacillus paramycoides. Furthermore, growth condition including temperature and pH were optimized for both bacterial strains, showed maximum growth at temperature 30ºC and at optimum pH 7.5 and 6.5 respectively. It is concluded that indigenous bacterial strains isolated from metal contaminated industrial effluent use their innate ability to transform toxic heavy metals to less or nontoxic form and can offer an effective tool for monitoring heavy metal contamination in the environment.

O cromo (VI), metal altamente tóxico, é um dos principais constituintes dos resíduos industriais. É liberado no solo e na água, causa problemas ambientais e de saúde de crescente preocupação pública em países em desenvolvimento como o Paquistão. O objetivo básico deste estudo foi o isolamento e a triagem de bactérias resistentes ao cromo de resíduos industriais coletados em Korangi e Lyari, Karachi (24˚52’46,0”N 66˚59’25,7”E e 24˚48’37,5”N 67˚06’52,6”E). Do total de 53 cepas isoladas, sete cepas bacterianas foram selecionadas por enriquecimento seletivo e identificadas com base em características morfológicas e bioquímicas. Essas cepas foram designadas como S11, S13, S17, S18, S30, S35 e S48, apresentaram alta resistência aos metais contra concentrações variáveis (100-1500 mg / l) de cromo. Já as cepas S35 e S48 foram identificadas por meio da sequência 16S rRNA e apresentaram 99% de similaridade com Bacillus paranthracis e Bacillus paramycoides. Além disso, as condições de crescimento incluindo temperatura e pH foram otimizadas e ambas as cepas bacterianas apresentaram crescimento máximo na temperatura de 30ºC, enquanto seu pH ótimo foi observado em 7,5 e 6,5, respectivamente. Conclui-se que o potencial de resistência dessas bactérias resistentes ao cromo pode ser efetivamente utilizado na remoção de cromo de efluentes industriais contaminados. Técnicas de base biológica usando bactérias ajudarão a fornecer métodos mais baratos e ecológicos de remoção, recuperação e desintoxicação de cromo.

Development of highly efficient electrocompetent cells for electroporation of Geobacillus thermoglucosidasius NCIMB 11955 / 生物工程学报

Geobacillus thermoglucosidasius is a kind of Gram-positive facultative anaerobic bacteria. The fast growth rate under high temperature and less susceptibility to microbial contamination enable G. thermoglucosidasius to be a desirable producer of biofuels and high-value-added chemicals for the next-generation industrial biotechnology. However, compared with the classical model strain Escherichia coli, the applications of G. thermoglucosidasius are hampered by its low transformation efficiency. This study aimed at obtaining competent cells with high transformation efficiency through inactivating restriction enzymes, adding cell membrane inhibitors and cell wall weakening agents. The results showed that the electro-transformation efficiency achieved 1.2×104 CFU/(μg DNA) by knocking out four genes encoding restriction enzymes. Adding a certain amount of tween 80, dl-threonine and glycine further increased the competent efficiency about 22.5, 44, and 334 times, respectively. The electro-transformation efficiency was enhanced to 4.6×106 CFU/(μg DNA) under the optimized conditions, laying a foundation for genetic manipulation and metabolic engineering of G. thermoglucosidasius.

Draft genome sequence of Exiguobacterium aurantiacum strain PN47 isolate from saline ponds, known as "Salar del Huasco", located in the Altiplano in the North of Chile

ABSTRACT In this report, we present a draft genome of 2,886,173 bp of an Exiguobacterium aurantiacum strain PN47 isolate from the sediment of a saline pond named "Salar del Huasco" in the Altiplano in the North of Chile. Strain PN47 encodes adaptive characteristics enabling survival in extreme environmental conditions of high heavy metal and salt concentrations and high alkalinity.

Microorganisms in Vacuum Stored Flower Bee Pollen

Contamination with sanitary microorganisms from Enterobacteriaceae, Pseudomonadaceae, Staphylococcaceae, Micrococcaceae and Bacillaceae families in flower bee pollen from Bulgaria after one-year vacuum-packed cold storage has been found. Dried flower bee pollens intended for human consumption were with high incidence rate of contamination with Pantoea sp. (P. agglomerans and P. agglomerans bgp6) (100%), Citrobacter freundii (47%), Proteus mirabilis (31.6%), Serratia odorifera (15.8%) and Proteus vulgaris (5.3%). Bee pollens were also positive for the culture of microorganisms from Staphylococcaceae, Micrococcaceae and Bacillaceae families: Staphylococcus hominis subsp hominis, Staphylococcus epidermidis, Arthrobacter globiformis, Bacillus pumilis, Bacillus subtilis and Bacillus amyloliquefaciens. It was concluded that, if consumed directly, the vacuum-packed cold stored dried bee pollen, harvested according hygienic requirements from bee hives in industrial pollution-free areas without intensive crop production, is not problem for healthy human.

Adsorption of Toxic Metals and Control of Mosquitos-borne Disease by Lysinibacillus sphaericus: Dual Benefits for Health and Environment / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>Assessment of the bacterium L. sphaericus as a dual-action candidate for biological control of mosquito-borne diseases and bioremediation of toxic metals.</p><p><b>METHODS</b>Larvae of the mosquito, C. quinquefasciatus, were first evaluated for metal tolerance and then exposed to 5 ppm cadmium, chromium, arsenic, and lead in assays together with seven strains of L. sphaericus. A probit regression analysis was used to estimate the LC(50) of Cd, Cr, As, and Pb to C. quinquefasciatus. An analysis of covariance and multifactorial ANOVA examined the metal biosorption and larvicidal properties of the seven strains of L. sphaericus.</p><p><b>RESULTS</b>We found that L. sphaericus adsorbed the toxic metal ions and was toxic against mosquito larvae. The L. sphaericus strain III(3)7 resulted in a larvae mortality of over 80% for all the tested metals. This strain also exhibited the capacity to adsorb 76% of arsenic, 32% of lead, 25% of chromium, and 7% of cadmium.</p><p><b>CONCLUSION</b>This study found combined metal adsorption and larval toxicity associated with three strains of L. sphaericus [III(3)7, OT4b.31, and CBAM5]. This suggests that a combination of these strains shows strong dual potential for biological control of mosquitos in heavy metal-contaminated areas and remediate the heavy metal contamination as well.</p>

Stability enhancement of urethanase from Lysinibacillus fusiformis by site-directed mutagenesis / 生物工程学报

Ethyl carbamate as a potential carcinogen commonly exists in traditional fermented foods and beverages. Enzymatic removal of ethyl carbamate from fermented foods and beverages is an efficient and safe method. In this study, we mutated urethanase from Lysinibacillus fusiformis SC02 on the Q328 site through computer aided design approaches. The half-life of resulting mutants Q328C and Q328V was detected to be 7.46 and 1.96 folds higher than that of the original enzyme, and Q328R presented better thermal-tolerance than the original urethanase when incubated at high temperature. The tolerance of Q328C to ethanol and acid also increased when compared with that of the original enzyme. The stability and tolerance to acid and ethanol of urethanase could be improved by modification on its Q328 site.

Thermophilic bacteria in Moroccan hot springs, salt marshes and desert soils

The diversity of thermophilic bacteria was investigated in four hot springs, three salt marshes and 12 desert sites in Morocco. Two hundred and forty (240) thermophilic bacteria were recovered, identified and characterized. All isolates were Gram positive, rod-shaped, spore forming and halotolerant. Based on BOXA1R-PCR and 16S rRNA gene sequencing, the recovered isolates were dominated by the genus Bacillus (97.5%) represented by B. licheniformis (119), B. aerius (44), B. sonorensis (33), B. subtilis (subsp. spizizenii (2) and subsp. inaquosurum (6)), B. amyloliquefaciens (subsp. amyloliquefaciens (4) and subsp. plantarum (4)), B. tequilensis (3), B. pumilus (3) and Bacillus sp. (19). Only six isolates (2.5%) belonged to the genus Aeribacillus represented by A. pallidus (4) and Aeribacillus sp. (2). In this study, B. aerius and B. tequilensis are described for the first time as thermophilic bacteria. Moreover, 71.25%, 50.41% and 5.41% of total strains exhibited high amylolytic, proteolytic or cellulolytic activity respectively.

Lipolytic Activity and Molecular Identification of Pseudomonas aeruginosa and Lysinibacillus sphaericus Isolated from Domestic Oil Rich Wastewater.

Microbial lipases have been heightened in bioremediation and various industries. Place and Duration of Study: Department of Microbiology, Ekiti State University, Ado-Ekiti, Ekiti State, Nigeria, between September 2010 and August 2011. To identify the lipolytic enzyme producing microbial strains in domestic oil rich wastewater, the 16S rRNA gene was amplified and sequenced. The sequences were used to identify the strains by comparing with related sequences in database using BLAST analysis. The enzyme activity was quantified by HPLC analysis. All the lipolytic bacteria showed appreciable growth rates in the wastewater (between 0.67 and 1.67 mg/day) within 5 days. The most effective lipolytic bacteria isolates in the oil-rich wastewater were two species of the genus Pseudomonas and one of Bacillus. Comparing the weights on the first day to the twelfth day values when lipolytic organisms were grown in palm oil, some appreciable increases in weight difference were recorded in some isolates: 28.3%, 7.84%, 4.44% and 6.98% for Pseudomonas, Staphylococcus, Bacillus and Klebsiella, respectively. The weight increase of each of the microbial cells in palm oil culture was usually lesser than what was obtained in the oil-rich wastewater culture. Two isolates showed high similar sequence (99%) to that of Pseudomonas aeruginosa and Lysinibacillus sphaericus, respectively. From palm oil, Lysinibacillus sp. produced various forms of fatty acids in the medium, including myristic acid (2.61%), palmitic acid (6.22%), stearic acid (5.18%) and arachidic (3.66%). These strains are versatile in utilizing the limited nutrient and had the ability to grow appreciably in the toxic condition (soap solution), suggesting that they may serve as candidates in treating dietary oil-rich wastewater.

The Effect of Temperature on Nitrate and Phosphate Uptake from Synthetic Wastewater by Selected Bacteria Species.

Aim: The aim of this study was to ascertain the effect of temperature on nutrient uptake ability of four bacterial species. Methodology: A total of four bacterial species (Klebsiella sp., Pseudomonas sp., Lysinibacillus sp. and Staphylococcus sp.) were used for the study. The media used for the investigation was synthetic wastewater. Four different temperatures (25ºC, 30ºC, 35ºC and 40ºC) were used for the investigation. The study was carried out under shake flasks conditions. Immediate after inoculation with the respective test bacterial species and every 24 h for a 96 h incubation time, aliquot wastewater samples were removed from the flasks for the estimation of total phosphate, nitrate, pH and growth rate, using standard procedures. Results: The results revealed phosphate and nitrate removal ranges of 10.84 % to 55.55 % and 90.67 % to 97.27 %, respectively in the presence of the Klebsiella sp. In the presence of the Pseudomonas sp, Lysinibacillus sp. and Staphylococcus sp., phosphate removals ranges of 0.36 % to 46.98 %, 11.89 % to 50.80 % and 2.74 % to 51.21 % were observed, respectively. For nitrate concentrations, removal levels that ranged from 2.19 % to 92.95 %, 0.97 % to 23.12 % and 7.56 % to 91.66 % were observed in the presence of Pseudomonas sp, Lysinibacillu ssp. and Staphylococcus sp., respectively. All the test bacterial species showed some measure of efficiency in phosphate removal. For nitrate removal, the Lysinibacillus sp. did not exhibit remarkable nitrate removal ability at any of the temperatures. In addition, the optimum temperatures for phosphate removals were observed to be 30ºC to 40ºC for the Klebsiella sp. and Pseudomonas sp; and 30ºC to 35ºC for the Lysinibacillus sp. and Staphylococcus sp. For nitrate removal, optimum temperatures for removal were observed to be 25ºC to 40ºC, for the Klebsiella sp and 25ºC to 35ºC, for the Pseudomonas sp. and Staphylococcus sp. Conclusion: The study was able to reveal the optimum temperatures for phosphate and nitrate uptake in synthetic wastewater by the test bacterial species.

Cyclodextrin glucanotransferase immobilization onto functionalized magnetic double mesoporous core-shell silica nanospheres

Background Cyclodextrin glucanotransferase (CGTase) from Amphibacillus sp. NPST-10 was covalently immobilized onto amino-functionalized magnetic double mesoporous core-shell silica nanospheres (mag@d-SiO2@m-SiO2-NH2), and the properties of the immobilized enzyme were investigated. The synthesis process of the nanospheres included preparing core magnetic magnetite (Fe3O4) nanoparticles, coating the Fe3O4 with a dense silica layer, followed by further coating with functionalized or non-functionalized mesoporous silica shell. The structure of the synthesized nanospheres was characterized using TEM, XRD, and FT-IR analyses. CGTase was immobilized onto the functionalized and non-functionalized nanospheres by covalent attachment and physical adsorption. Results The results indicated that the enzyme immobilization by covalent attachment onto the activated mag@d-SiO2@m-SiO2-NH2, prepared using anionic surfactant, showed highest immobilization yield (98.1%), loading efficiency (96.2%), and loading capacity 58 µg protein [CGTase]/mg [nanoparticles]) which were among the highest yields reported so far for CGTase. Compared with the free enzyme, the immobilized CGTase demonstrated a shift in the optimal temperature from 50°C to 50-55°C, and showed a significant enhancement in the enzyme thermal stability. The optimum pH values for the activity of the free and immobilized CGTase were pH 8 and pH 8.5, respectively, and there was a significant improvement in pH stability of the immobilized enzyme. Moreover, the immobilized CGTase exhibited good operational stability, retaining 56% of the initial activity after reutilizations of ten successive cycles. Conclusion The enhancement of CGTase properties upon immobilization suggested that the applied nano-structured carriers and immobilization protocol are promising approach for industrial bioprocess for production of cyclodextrins using immobilized CGTase.

A new low molecular mass alkaline cyclodextrin glucanotransferase from Amphibacillus sp. NRC-WN isolated from an Egyptian soda lake

Background: Cyclodextrin glucanotransferase (CGTase) is one of the most industrially important enzymes used in the commercial production of cyclodextrins (CDs). Alkaliphilic bacteria have attracted much interest in the last few decades because of their ability to produce extracellular enzymes that are active and stable at high pH values. Here, we report the isolation of a new CGTase from alkaliphilic bacteria collected from Egyptian soda lakes and describe the purification and biochemical characterization of this CGTase. Results: Screening for CGTase-producing alkaliphilic bacteria from sediment and water samples collected from Egyptian soda lakes located in the Wadi Natrun valley resulted in the isolation of a potent CGTase-producing alkaliphilic bacterial strain, designated NRC-WN. Strain NRC-WN was belonging to genus Amplibacullus by 16S rDNA sequence analysis (similarity: ca. 98%). Among the tested nitrogen and carbon sources, peptone (0.15%, w/v) and soluble starch (0.4%, w/v) allowed maximal CGTase production by Amphibacillus sp. NRC-WN. CGTase was successfully purified from Amphibacillus sp. NRC-WN up to 159.7-fold through a combination of starch adsorption and anion exchange chromatography, resulting in a yield of 84.7%. SDS-PAGE analysis indicated that the enzyme was purified to homogeneity and revealed an estimated molecular mass of 36 kDa, which makes it one of the smallest CGTases reported in the literature. The purified enzyme exhibited maximum activity at 50ºC and was stable up to 70ºC, retaining 93% of its initial activity after treatment for 1 hr. Furthermore, Ca2+ ions (10 mM) significantly enhanced the thermal stability of the CGTase. The purified enzyme was active and stable over a wide pH range, showing maximal activity at pH 9.5. The enzyme was significantly stimulated by Zn2+, Ca2+ and Co2+ but was completely inhibited in the presence of Fe3+ and mercaptoethanol. The Km and Vmax values of the purified CGTase were estimated to be 0.0434 mg/ml and 3,333.3 mg β-CD/ml/min, respectively. β-CD was the predominant product of starch degradation by the Amphibacillus sp. NRC-WN CGTase, followed by α-and γ-CDs. Conclusions: A new low molecular mass alkaline CGTase was purified from a newly identified alkaliphilic Amphibacillus sp. NRC-WN isolate from the Egyptian soda lakes. The enzyme showed promising thermal and pH stability and a high affinity toward starch as a natural substrate.

Immobilization of cyclodextrin glucanotransferase on aminopropyl-functionalized silica-coated superparamagnetic nanoparticles

Background: Cyclodextrin glycosyltransferase (CGTase) from Amphibacillus sp. NPST-10 was successfully covalently immobilized on aminopropyl-functionalized silica coated superparamagnetic nanoparticles; and the properties of immobilized enzyme were investigated. The synthesis process included preparing of core magnetic magnetite (Fe3O4) nanoparticles using solvothermal synthesis; followed by coating of Fe3O4 nanoparticles with dense amino-functionalized silica (NH2-SiO2) layer using in situ functionalization method. The structure of synthesized Fe3O4@NH2-SiO2 nanoparticles was characterized using TEM, XRD, and FT-IR analysis. Fe3O4@NH2-SiO2 nanoparticles were further activated by gluteraaldehyde as bifunctional cross linker, and the activated nanoparticles were used for CGTase immobilization by covalent attachment. Results: Magnetite nanoparticles was successfully synthesized and coated with and amino functionalized silica layer (Fe3O4/NH2-SiO2), with particle size of 50-70 nm. The silica coated magnetite nanoparticles showed with saturation magnetization of 65 emug-1, and can be quickly recovered from the bulk solution using an external magnet within 10 sec. The activated support was effective for CGTase immobilization, which was confirmed by comparison of FT-IR spectra of free and immobilized enzyme. The applied approach for support preparation, activation, and optimization of immobilization conditions, led to high yields of CGTase immobilization (92.3%), activity recovery (73%), and loading efficiency (95.2%); which is one of the highest so far reported for CGTase. Immobilized enzyme showed shift in the optimal temperature from 50 to 55ºC, and significant enhancement in the thermal stability compared with free enzyme. The optimum pH for enzyme activity was pH 8 and pH 7.5 for free and immobilized CGTase, respectively, with slight improvement of pH stability of immobilized enzyme. Furthermore, kinetic studies revealed that immobilized CGTase had higher affinity toward substrate; with k m values of 1.18 ± 0.05 mg/ml and 1.75 ± 0.07 mg/ml for immobilized and free CGTase, respectively. Immobilized CGTase retained 87% and 67 of its initial activity after 5 and 10 repeated batches reaction, indicating that immobilized CGTase on Fe3O4/NH2-SiO2 had good durability and magnetic recovery. Conclusion: The improvement in kinetic and stability parameters of immobilized CGTase makes the proposed method a suitable candidate for industrial applications of CGTase. To best of our knowledge, this is the first report about CGTase immobilization on silica coated magnetite nanoparticles.

Novel organic solvent-tolerant esterase isolated by metagenomics: insights into the lipase/esterase classification / Nueva esterasa tolerante a los solventes orgánicos aislada por metagenómica: ideas sobre la clasificación de las esterasas/lipasas

In order to isolate novel organic solvent-tolerant (OST) lipases, a metagenomic library was built using DNA derived from a temperate forest soil sample. A two-step activity-based screening allowed the isolation of a lipolytic clone active in the presence of organic solvents. Sequencing of the plasmid pRBest recovered from the positive clone revealed the presence of a putative lipase/esterase encoding gene. The deduced amino acid sequence (RBest1) contains the conserved lipolytic enzyme signature and is related to the previously described OST lipase from Lysinibacillus sphaericus 205y, which is the sole studied prokaryotic enzyme belonging to the 4.4 a/ß hydrolase subgroup (abH04.04). Both in vivo and in vitro studies of the substrate specificity of RBest1, using triacylglycerols or nitrophenyl-esters, respectively, revealed that the enzyme is highly specific for butyrate (C4) compounds, behaving as an esterase rather than a lipase. The RBest1 esterase was purified and biochemically characterized. The optimal esterase activity was observed at pH 6.5 and at temperatures ranging from 38 to 45 °C. Enzymatic activity, determined by hydrolysis of p-nitrophenyl esters, was found to be affected by the presence of different miscible and non-miscible organic solvents, and salts. Noteworthy, RBest1 remains significantly active at high ionic strength. These findings suggest that RBest1 possesses the ability of OST enzymes to molecular adaptation in the presence of organic compounds and resistance of halophilic proteins.

Con el fin de aislar nuevas variantes de lipasas tolerantes a solventes organicos (OST), se construyo una libreria metagenomica a partir de ADN obtenido de una muestra de suelo de bosque templado. A traves de un monitoreo en dos etapas, basado en la deteccion de actividades, se aislo un clon con actividad lipolitica en presencia de solventes organicos. La secuenciacion del plasmido pRBest recuperado del clon positivo revelo la presencia de un gen codificante de una hipotetica lipasa/esterasa. La secuencia deducida de amino acidos (RBest1) contiene los motivos conservados de enzimas lipoliticas y esta relacionada con la lipasa OST previamente descrita de Lysinibacillus sphaericus 205y, que es la unica enzima procariota estudiada perteneciente al subgrupo 4.4 de a/ß hidrolasas (abH4.04). Estudios in vivo e in vitro sobre la especificidad de sustratos de RBest1, utilizando triacil-gliceroles o p-nitrofenil-esteres, respectivamente, revelaron que la enzima es altamente especifica para compuestos butiricos (C4), comportandose como una esterasa y no como una lipasa. La esterasa RBest1 fue purificada y caracterizada bioquimicamente. La actividad optima de esterasa fue observada a pH 6,5 y las temperaturas optimas fueron entre 38 y 45 °C. Se establecio que la actividad enzimatica, determinada por hidrolisis de p-nitrofenil esteres, es afectada en presencia de diferentes solventes organicos miscibles y no miscibles, y tambien sales. Notoriamente, RBest1 permanece significativamente activa a elevadas fuerzas ionicas. Estos hallazgos sugieren que RBest1 posee la capacidad de las enzimas OST de la adaptacion molecular en presencia de compuestos organicos, asi como la resistencia de las proteinas halofilas.

Mortalidad en larvas de Culex quinquefasciatus y Anopheles albimanus (díptera: culicidae), causada con un producto de Bacillus sphaericus (bacteria: bacillaceae) en presentación granulada en condiciones experimentales / Larval Mortality in Culexquinquefasciatus and Anopheles albimanus (diptera: culicidae), Caused with a Bacillus sphaericus (bacteria: bacillaceae) Granulated Product in Experimental Conditions

El objetivo de este estudio fue ensayar una serie de concentraciones de un producto granulado preparado con Bacillus sphaericus, sobre larvas de Culex quinquefasciatus y Anopheles albimanusen condiciones de laboratorio. Se utilizaron once concentraciones (20, 40, 60, 80,100, 120, 140, 160, 180, 200 y 500 ppm) sobre larvas de An. albimanus, y ocho concentraciones diez veces menores (2, 4, 6, 8, 10, 12, 14 y 16 ppm) sobre larvas de Cx. quinquefasciatus.Se utilizaron 60 larvas y un control con 20 larvas por concentración. El tiempo de exposición fue de 48 h, a una temperatura de 28 ± 2 ºC. Para estimar las concentraciones letales 50 y 95 se utilizó la prueba Probit. Se encontró una CL95 de B. sphaericus entre 6,45 y 7,28 ppm para larvas de Cx. quinquefasciatus; mientras que en larvas de An. albimanus se observó una CL95entre 450,56 y 466,76 ppm...

The purpose of this study was to assay a series of concentrations of a granulated productprepared with Bacillus sphaericus on Culexquinquefasciatus and Anopheles albimanus larvae inlaboratory conditions. Eleven concentrations (20, 40, 60, 80, 100, 120, 140, 160, 180, 200,500 ppm) were used on An. Albimanus larvae and eight concentrations ten times smaller (2,4, 6, 8, 10, 12, 14, 16 ppm) were used on Cx. quinquefasciatus larvae. Sixty (60) larvae and acontrol with 20 larvae were used per concentration. The time of exposure was of 48 hours ata laboratory temperature of 28 ± 2 ºC. LC50 and LC95 were determined through the Probittests. A LC95 of B. sphaericus was found between 6,45 and 7,28 ppm for Cx. quinquefasciatuslarvae; whereas LC95 was observed between 450.56 and 466.76 ppm in An. albimanus larvae...

O objetivo deste estudo foi testar uma série de concentrações de um produto granulado preparadocom Bacillus sphaericus, sobre larvas de Culex quinquefasciatus e Anopheles albimanusem condições de laboratório. Utilizaram-se onze concentrações (20, 40, 60, 80, 100, 120,140, 160, 180, 200 e 500 ppm) sobre larvas de An. albimanus, e oito concentrações dez vezesmenores (2, 4, 6, 8, 10, 12, 14 e 16 ppm) sobre larvas de Cx. quinquefasciatus. Utilizaram-se60 larvas e um controle com 20 larvas por concentração. O tempo de exposição foi de 48h,a uma temperatura de 28 ± 2 ºC. Para estimar as concentrações letais 50 e 95 utilizou-seo teste Probit. Encontrou-se uma CL95 de B. sphaericus entre 6,45 e 7,28 ppm para larvasde Cx. quinquefasciatus; enquanto que em larvas de An. Albimanus observou-se uma CL95entre 450,56 e 466,76 ppm...

Isolation and characterization of novel potent Cr(VI) reducing alkaliphilic amphibacillus sp. ksuCr3 from hypersaline soda lakes

A strain KSUCr3 with extremely high Cr(VI)-reducing ability under alkaline conditions was isolated from hypersaline soda lakes and identified as Amphibacillus sp. on the basis of 16S rRNA gene sequence analysis. The results showed that Amphibacillus sp. strain KSUCr3 was tolerance to very high Cr(VI) concentration (75 mM) in addition to high tolerance to other heavy metals including Ni2+ (100 mM), Mo2+ (75 mM), Co2+ (5 mM), Mn2+ (100 mM), Zn2+ (2 mM), Cu2+ (2 mM) and Pb (75 mM). Strain KSUCr3 was shown to be of a high efficiency in detoxifying chromate, as it could rapidly reduce 5 mM of Cr(VI) to a non detectable level over 24 hrs. In addition, strain KSUCr3 could reduce Cr(VI) efficiently over a wide range of initial Cr(VI) concentrations (1-10 mM) in alkaline medium under aerobic conditions without significant effect on the bacterial growth. Addition of glucose, NaCl and Na2CO3 to the culture medium caused a dramatic increase in Cr(VI)-reduction by Amphibacillus sp. strain KSUCr3. The maximum chromate removal was exhibited in alkaline medium containing 1.5 percent Na2CO3, 0.8 percent glucose, and 1.2 percent NaCl, at incubation temperature of 40ºC and shaking of 100 rpm. Under optimum Cr(VI) reduction conditions, Cr(VI) reduction rate reached 237 uMh¹ which is one of the highest Cr(VI) reduction rate, under alkaline conditions and high salt concentration, compared to other microorganisms that has been reported so far. Furthermore, the presence of other metals, such as Ni2+, Co2+, Cu2+ and Mn2+ slightly stimulated Cr(VI)-reduction ability by the strain KSUCr3.The isolate, Amphibacillus sp. strain KSUCr3, exhibited an ability to repeatedly reduce hexavalent chromium without any amendment of nutrients, suggesting its potential application in continuous bioremediation of Cr(VI). The results also revealed the possible isolation of potent heavy metals resistant bacteria from extreme environment such as hypersaline soda lakes.

Lipase production and growth modeling of a novel thermophilic bacterium: aneurinibacillus thermoaerophilus strain AFNA

Aneurinibacillus thermoaerophilus strain AFNA as a novel isolated extracellular thermostable organic solvent tolerant lipase producing bacterium was employed in the present study. The lipase production of strain AFNA and its correlation with bacterial growth was studied via a modeling assessment by response surface methodology (RSM) and artificial neural network (ANN) techniques. The best achieved models were multilayer full feed forward incremental back propagation network and modified cubic response surface model (mRSM) using backward elimination. The highest lipase specific activity (13.1 Umg-1) and bacterial growth (OD600 = 3.0) were obtained at technically similar: growth temperature (53 and 53ºC), inoculum size (2.6 and 3.0 percent), agitation rate (118 and 115 rpm) and initial pH (7.0 and 7.2) but different medium volume (139 and 87 ml) and incubation period (48 and 38 hrs), respectively. In addition, the importance of effective parameters on the bacterial growth and lipase production was studied where pH and inoculum size were the most and the least effective factors, respectively. Significant correlation between lipase production and bacterial growth was observed when Bivariate correlation was employed to analyse the data. As a conclusion, lipase production was the result of a synergistic combination of effective parameters interactions and these parameters were in equilibrium.

The high ethanol tolerance in a thermophilic bacterium Anoxybacillus sp. WP06 / 生物工程学报

Anoxybacillus sp. WP06 is a thermophilic (optimum temperature for growth, 60 degrees C), facultative anaerobe. Strain WP06 is able to utilize a wide range of carbon sources such as glucose, xylose, arabinose, starch, maltose and sorbitol. Anaerobically, glucose and xylose were fermented to ethanol as minor products. Unlike most thermophilic bacteria isolated to date, strain WP06 is tolerant (maintained viability) to high ethanol concentrations up to 15% at 60 degrees C. The growth rate was slightly inhibited at 8% ethanol. The observation that strain WP06 exhibits higher tolerance of 15% ethanol at 60 degrees C exploits the level of ethanol tolerance in thermophilic bacteria. Strain WP06 may be candidate for mechanisms of ethanol tolerance in thermophilic bacteria.