Screening of bacterial extracellular xylanase producers with potential for cellulose pulp biobleaching

In this study, two hundred fifty-seven bacterial isolates from a suppressive soil library were screened to study their secretion of alkali-thermostable xylanases for potential use in cellulose pulp biobleaching. Xylanase activity was evaluated in solid and liquid media using xylan as the carbon source. Isolates were initially evaluated for the degradation of xylan in solid media by the congo red test. Selected strains were evaluated in liquid media for enzymatic activity and determination of total protein concentration using a crude protein extract (CPE). An isolate identified as Bacillus species TC-DT13 produced the highest amount of xylanase (1808 U mL-1). The isolate was active and stable at 70°C and pH 9.0, conditions which are necessary for the paper industry. This isolate can grow and produce xylanase in medium containing wheat fiber as a substrate. The CPE of this isolate was used in preliminary testing on cellulose pulp bleaching; enzyme treatment of the pulp resulted in a 5% increase of whiteness.

Community structure and diversity of soil bacteria in rhizosphere of Salvia miltiorrhiza and Salvia miltiorrhiza f. alba based on pyrosequencing / 中国中药杂志

Rhizosphere bacteria play a vital role in plant nutrition absorption,growth and disease resistance. In this study,high-throughput sequencing technology was used to analyze the rhizosphere bacterial communities of Salvia miltiorrhiza and S. miltiorrhiza f. alba. Moreover,the function of dominant rhizosphere bacterial communities was analyzed. We found that Sphingobacteriales,Sphingomonadales and Nitrosomonadaceae were both dominant and specific bacteria in the rhizosphere of S. miltiorrhiza. The main functions of dominant rhizosphere bacteria communities in both species include promoting transformation of soil nutrients,improving plant immunity and ability of stress tolerance. This study was the first to compare rhizobacterial communities structure and function of S. miltiorrhiza and S. miltiorrhiza f. alba,which provided a new theoretical reference for studing the rhizosphere mechanism of healthy S. miltiorrhiza planting in the future.

Colour changes as an indicator for estimating fungal growth in solid state fermentation

@#Aims:In this study, measurement of colour changes during solid state fermentation (SSF) are presented as one of the potential techniques that can be used to describe growth, complementary to other biomass estimation, such as weight of fungus, spores concentration, organic matter loss, glucosamine and enzyme activity, which is directly related to growth.Methodology and results: In this study, fungal fermentation of Aspergillus awamoriand A.oryzaeare carried out on complex heterogeneous solid media; wheat bran, soybean hull and rapeseed meal, which are constituted of various soluble and insoluble solid particles. Fermented mass was extracted using distilled water to obtain a cell free extract, which canbe determined quickly and accurately using UV-Visible spectrophotometermeasured absorbance at 300 nm. The results showed a significant correlation between colours produced from fungal SSF and the concentration of spores, weight of fungus cells, organic matter loss, glucosamine and enzyme activity. We found that the colour density proportionally increased when the studied parameters mentioned above increased.For the growth of A. awamoriand A. oryzaeon wheat bran, soybean hulls and rapeseed meal, it was confirmed that colour production was directly proportional to fungal growth. In general, colour-based methods seem to be the most promising approach for biomass estimation in SSF.Conclusions, significance and impacts of study:The theory of measuring colour changes in SSF by UV-visible spectroscopy demonstrates that the colour method gives some valuableinformation than just obtaining a visual observation or spore count to describe growth of fungal mycelium in SSF. The ideas obtained from this exercise might provide a quick and convenient method for quality control of fungal growth. The advantages of this method are that the procedure is simple to carry out, it is non-destructive and no special and expensive reagents are required and the process is very cheap.This newapproach is an important complimentation to the existing techniques especially for basic studies.

Draft genome sequence of Streptomyces sp. strain F1, a potential source for glycoside hydrolases isolated from Brazilian soil

ABSTRACT Here, we show the draft genome sequence of Streptomyces sp. F1, a strain isolated from soil with great potential for secretion of hydrolytic enzymes used to deconstruct cellulosic biomass. The draft genome assembly of Streptomyces sp. strain F1 has 69 contigs with a total genome size of 8,142,296 bp and G + C 72.65%. Preliminary genome analysis identified 175 proteins as Carbohydrate-Active Enzymes, being 85 glycoside hydrolases organized in 33 distinct families. This draft genome information provides new insights on the key genes encoding hydrolytic enzymes involved in biomass deconstruction employed by soil bacteria.

Comparison of various culture media effectiveness in the isolation of bacteria from Pekan peat swamp forest soil

Aims: Previously described as non-favorable-microbial habitat, peat swamp forest has its own features, which are extremely acidic, poor in nutrient, water-logged and anoxic environment where rate of decomposition of plant litters is quiet slow. Interestingly, current research has proven that there is diversity of microbial communities in this ecosystem. The main objective of this study is to isolate bacteria from Pekan peat swamp forest soil that play a role in the decomposition of plant litters through cultivation on different agar-based medium. The success of isolation of bacteria from this neglected habitat could open the opportunity in unleashing the specific role of bacteria in peat swamp plant litter degradation as well as potential biotechnological application of these bacteria in lignocellulose-related industry. Methodology and results: To mimic the peat condition that is low in nutrient and comprised of plant debris, M1 and peat agar supplemented with cellulose, glucose, lignin and xylan were used. Specifically, for the isolation of actinomycetes, dry and wet heat pre-treatments were applied to the soil samples. Then, the samples were cultivated on three different agars which were oatmeal agar as well as M1 and peat agar supplemented with glucose. Enrichment method was applied in the isolation of cellulase-producing bacteria. It was found that higher number of bacteria and actinomycetes were successfully isolated from peat agar, followed by oatmeal agar and M1. In fact, more actinomycetes were isolated from soil that was treated with wet heat pre-treatment compared to dry heat pre-treatment and on peat agar compared to M1 and oatmeal agar. This finding is promising, indicating that the application of peat water in the agar-based medium is useful to mimic the actual environment of peat swamp and increase the possibility to isolate indigenous bacteria. Primary screening of isolates from samples enriched with carboxymethyl cellulose (CMC) showed positive result of decolourisation zone on Azo-CM-Cellulose agar indicating the ability of isolates to degrade cellulose compound. Conclusions, significance and impacts of study: The study indicates the effectiveness of different culture media in successful isolation of bacteria including actinomycetes. Using the enrichment method, bacteria that are able to degrade cellulose compound was successfully isolated even though it is well known that plant litter degradation in the peat swamp environment happens at very slow rates.

Biodiversity of Antimicrobial-Producing Actinomycetes Strains Isolated from Dry Dipterocarp Forest Soil in Northeast Thailand

The increasing use of antibiotics has led to the development of drug-resistant microorganisms. The emergence of resistant strains has compromised the treatment and control of infectious diseases. As a result, the search and development of a novel class of antibiotic drugs are required. Actinomycetes have been recognized as a richest source of secondary metabolites including antibiotics. The aim of this study was to investigate the diversity of antibiotic-producing soil Actinomycetes from dry dipterocarp forest in Northeast of Thailand. The soil from this area has been known for its poor in nutrients and highly acidic with pH values around 4.5. In such a harsh condition, soil-inhabiting Actinomycetes elevate their protective mechanisms by inducing the production of antimicrobials and other defense compounds. Therefore, dry dipterocarp forest could be served as a potential source for the screening of the novel antimicrobial drugs. Twelve antibiotic-producing strains isolated from soil in Suranaree University of Technology produce antimicrobial agents which are active against wide range of test pathogens including methicillin-resistant Staphylococcus aureus (MRSA). Based on 16S rRNA gene analysis, these strains are close affiliated with the genus Streptomyces (11 isolates) and Nonomuraea (1 isolate). Most of soil isolates show narrow antimicrobial spectrum activity against Gram-positive bacteria. Two isolates, PJ36 and PJ95, exhibit broad antimicrobial spectrum against Gram-positive bacteria, Gram-negative bacteria and yeasts. Phylogenetic tree analysis of 16S rDNA reveals that isolates PJ33, PJ36, PJ43, PJ51, PJ75, PJ76, PJ77, PJ85, PJ88 and PJ95 strains are not cluster with others strain of Streptomyces. They represent a distinct phyletic line which might be suggested the novel strains. This study was the first attempted to isolate antibiotic-producing Actinomycetes from dry dipterocarp forest soil in Northeast Thailand. Most of soil isolates (8 strains) obtained from this study were active against methicillin-resistant Staphylococcus aureus (MRSA). These isolates could be used for the development of new drugs to combat antibiotic resistances.

Isolation, characterization and growth kinetics of chaotrope induced water stress tolerant bacteria from soils of Thar Desert.

Chaotropic compounds that freely traverse biological membranes and do not affect turgor are powerful mediators of water stress. The present study was initiated to isolate, identify and characterize the Chaotrope tolerant bacteria from soil of Thar Desert. Bacteria were isolated from soil samples, collected from the surface of sand dunes, suspended in water contained 2.5 x 106 bacteria g-1 of soil while alcohol suspended soil had 4.4 x 104 bacteria g-1. The eleven bacterial isolates studied, for the tolerance was found tolerant to 10 % of alcohol, 14 % NaCl and 26 % glycerol and 9 out of 11 isolates were found to be gram positive. More than 50 % of isolates belonged to Bacillus species while Cornybacterium, Acinobacter, Aeromonas and Staphylococcus were also present. Growth kinetic studies revealed that under highly stressed conditions of alcohol and temperature, the generation time was reduced as compared to generation time in plain medium. A rise in incubation temperature and concentration of alcohol added in growth medium resulted in reduction in bacterial population. All Chaotropic solute tolerant bacteria were also tolerant to water stress induced by Halotropes and Kosmotrophes. This study suggests that non saline soil /sand dunes may be a common source for the isolation of bacteria tolerant to Chaotropic, Halotropic and Kosmotropic solutes up to a greater extent, and might help to resolve the general strategy adopted by microbes to thwart desiccation induced by various types of solutes.

Effect of phosphogypsum amendment on soil physico-chemical properties, microbial load and enzyme activities.

Phosphogypsum (PG) is produced as a solid waste from phosphatic fertilizer plants. The waste slurry is disposed off in settling ponds or in heaps .This solid waste is now increasingly being used as a calcium supplement in agriculture. This study reports the effect of PG amendment on soil physico chemical properties, bacterial and fungal count and activities of soil enzymes such as invertase, cellulase and amylase over an incubation period of 28 days. The highest mean percent carbon loss (55.98%) was recorded in 15% PG amended soil followed by (55.28%) in 10% PG amended soil and the minimum (1.68%) in control soil. The highest number of bacterial colonies (47.4 CFU g-1 soil), fungal count (17.8 CFU g-1 soil), highest amylase activity (38.4 ?g g-1 soil hr-1) and cellulase activity (38.37 ?g g-1 soil hr-1) were recorded in 10% amended soil . Statistically significant difference (p<0.05) has been recorded in the activities of amylase and cellulase over the period of incubation irrespective of amendments. Considering the bacterial and fungal growth and the activities of the three soil enzymes in the control and amended sets, it appears that 10% PG amendment is optimal for microbial growth and soil enzyme activities.

Selection and Efficacy of Soil Bacteria Inducing Systemic Resistance Against Colletotrichum orbiculare on Cucumber

Soil bacteria were screened for the ability to control cucumber anthracnose caused by Colletotrichum orbiculare through induced systemic resistance (ISR). Sixty-four bacterial strains having in vitro antifungal activity were used for selecting ISR-inducing strains in cucumber. Cucumber seeds (cv. Baeknokdadagi) were sown in potting mixtures incorporated with the soil bacteria, at a rate of ca. 10(8) cells per gram of the mixture. Two week-old plants were then transplanted into the steam-sterilized soil. Three leaf-stage plants were inoculated with a conidial suspension (5x10(5) conidia/ml) of C. orbiculare. Diseased leaf area (%) and number of lesions per cm2 leaf were evaluated on third leaves of the plants, 5~6 days after inoculation. Among 64 strains tested, nine strains, GC-B19, GC-B35, GK-B18, MM-B22, PK-B14, RC-B41, RC-B64, RC-B65, and RC-B77 significantly (P = 0.05) reduced anthracnose disease compared to the untreated control. In contrast, some bacterial strains promoted susceptibility of cucumber to the disease. From the repeated experiments using the nine bacterial strains, GC-B19, MM-B22, PK-B14, and RC-B65 significantly (P = 0.05) reduced both diseased leaf area (%) and number of lesions per cm2 leaf in at lease one experiment. These strains with control efficacy of 37~80% were determined to be effective ISR-inducing strains.

Screening for In Vitro Antifungal Activity of Soil Bacteria Against Plant Pathogens

Antifungal bacteria for biological control of plant diseases or production of novel antibiotics to plant pathogens were isolated in 1997 from various soils of Ansung, Chunan, Koyang, and Paju in Korea. Sixty-four bacterial strains pre-screened from approximately 1,400 strains were tested on V-8 juice agar against eight plant pathogenic fungi using in vitro bioassay technique for inhibition of mycelial growth. Test pathogens were Alternaria mali, Colletotrichum gloeosporioides, C. orbiculare, Fusarium oxysporum f. sp. cucumerinum, F. oxysporum f. sp. lycopersici, Magnaporthe grisea, Phytophthora capsici, and Rhizoctonia solani. A wide range of antifungal activity of bacterial strains was found against the pathogenic fungi, and strain RC-B77 showed the best antifungal activity. Correlation analysis between inhibition of each fungus and mean inhibition of all eight fungi by 64 bacterial strains revealed that C. gloeosporioides would be best appropriate for detecting bacterial strains producing antibiotics with potential as biocontrol agents for plant pathogens.

Effect of stachyose on microbiotic disequilibrium in rhizospheric soil of Rehmannia glutinosa / 中草药

Objective To testify the screening function of stachyose on soil bacteria by investigating the bacterial culture in ammonium stachyose medium. Methods The turbidimetry was used to determine the absorbance of microbial suspension at 600 nm per 2 h under the same initial concentration of the microbial suspension and to draw their growth curves. Results Most of soil bacteria utilized stachyose ineffectively, while only a few of them grown well in ammonium stachyose medium. Conclusion Since the major soil bacteria can not take stachyose fully as their energy resources, the species and quantity of rhizobacteria may decrease largely and only a few that utilized stachyose better can develop vigorously. Those rhizobateria with better utilization of stachyose may multiply so rapidly as potential ones in the rhizosphere of Rehmannia glutinosa that the disequilibrium of soil microorganism appears.

Effects of inoculation with soil bacteria on growth of Rehmannia glutinosa in tube and potted plantlets / 中草药

Objective To investigate the cause of continuous cropping obstacle of Rehmannia glutinosa and screen beneficial bacteria.Methods In vitro cultured plantlets and potted plants were inoculated with different isolated soil bacteria. The plants were harvested and weighted in 30 and 60 d,respectively.Results In the in vitro culture experiment,11 out of 48 strains displayed promoting action on the growth of plantlets,and 11 other strains showed inhibitory or lethal action.In the potted test,16 strains showed promoting action and 13 strains showed suppressing or lethal action.Conclusion Soil bacteria influence the growth of R.glutinosa significantly.The flora of rhizosphere bacteria may be disturbed by the cultivation of R.glutinosa and inoculation of beneficial bacteria might be effective on the resolution of continuous cropping obstacle of R.glutinosa.

Study on Effect Factor of the Production of Catechol-type Siderophores Secreted by a Strain of Soil Bacteria / 微生物学通报

Catechol-type siderophores secreted by a strain of soil bacteria in three different medium were assayed by two high-resolution TLC.The results showed different medium had a significant effect on the secretion of catechol-type siderophores,and in three different medium strain S1 produced different catechol-type siderophores.The effect of Al~(3+) on Catechol-type siderophores by S1 were also assayed.The results showed Al~(3+)had a significant stimulation on the secretion of catechol-type siderophores.Moreover,Al~(3+)could to some extent counteract the repression of Fe~(2+)on siderophores production.In KMB medium four catechol-type siderophores were identified and all ones except for 2,3-dihydroxybenzoic acid(2,3-DHBA) had high affinity for Al~(3+).

THE STUDY OF RELATIONSHIP BETWEEN THE MOVEMENT OF SOIL BACTERIAL NUMBER AND ECOLOGICAL FACTORS ON THE LEYMUS CHINENSIS GRASSLAND / 微生物学通报

This paper preliminary studied the movement of soil bacterial number, and the relationship with 8 kinds of ecological factors. The result indicated: soil bacterial number only appears a biggest value in one year (2. 67?10-7个 individual g-1 dry soil). Among 8 kinds of ecological factors, soil water content, temperature, hydrolyted nitrogen, quick acting postossium and active organic matter have straight relationship with siol bacteria, and have negative relationship with soil pH, electric conduct rate, effective phosphorus. The component analysis indicated that soil water content, temperature, electric conduct rate, active organic matter are principal effective factors.

Detoxification of mercury and organomercurials by nitrogen-fixing soil bacteria.

Minimal inhibitory concentration values of HgCl2 and 5 organomercurials were determined against 24 mercury-resistant N2-fixing soil bacteria previously isolated from soil and identified in our laboratory. These bacterial strains also displayed multiple antibiotic resistant properties. Typical growth pattern of a highly mercury-resistant Beijerinckia sp (KDr2) was studied in liquid broth supplemented with toxic levels of mercury compounds. Four bacterial strains were selected for determining their ability to volatilize mercury and their Hg-volatilizing capacity was different. Cell-free extracts prepared from overnight mercury-induced cells catalyzed Hg2+-induced NADPH oxidation. Specific activities of Hg2+-reductase which is capable of catalyzing conversion of Hg2+ →Ηg (o) of 10 Hg-resistant bacterial strains are also reported.