Molecular authentication, metabolite profiling and in silico-in vitro cytotoxicity screening of endophytic Penicillium ramusculum from Withania somnifera for breast cancer therapeutics.

In the present study, we isolated a potent endophytic fungus from the roots of Withania somnifera. The endophytic fungal strain was authenticated as Penicillium ramusculum SVWS3 based on morphological and molecular sequencing using four gene data and phylogenetic analyses. In vitro cytotoxicity studies unveiled the remarkable cytotoxic potential of the crude extract derived from P. ramusculum, exhibiting dose-dependent effects on MDA-MB-468 and MCF-7 cells. At a concentration of 100 µg/mL, the crude extract resulted in cell viability of 29.78% for MDA-MB-468 cells and 14.61% for MCF-7 cells. The IC50 values were calculated as 62.83 ± 0.93 µg/mL and 17.23 ± 1.43 µg/mL, respectively for MDA-MB-468 and MCF-7 cells. Caspase activation assay established the underlying mechanism of the crude extract depicting the activation of caspases 3 and 7, indicating the induction of apoptosis in MCF-7 cells. Chemotaxonomic profiling elucidated the ability of P. ramusculum to synthesize a diverse array of bioactive compounds, including Fasoracetam, Tryprostatin B, Odorinol, Thyronine, Brevianamide F, Proglumide, Perlolyrine, Tyrphostin B48, Baptifoline, etc. Molecular docking studies inferred that Baptifoline, Brevianamide F, Odorinol, Perlolyrine, Thyronine, Tryphostin B48, and Tryprostatin B were the lead compounds that could effectively interact with the five selected target receptors of breast cancer, further surpassing the positive controls analyzed. Pharmacokinetic profiling revealed that Baptifoline, Odorinol, and Thyronine depicted an excellent therapeutic profile of druggability. These findings collectively substantiate the anticancer activity of bioactive metabolites synthesized by P. ramusculum SVWS3. Hence, the endophytic P. ramusculum SVWS3 can be an authentic source for developing novel chemotherapeutic drug formulations. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-023-03906-3.

Bacillus tequilensis PKDN31 and Bacillus licheniformis PKDL10 -As double headed swords to combat Fusarium oxysporum f. sp. lycopersici induced tomato wilt.

Wilt disease, caused by Fusarium oxysporum. f. sp. lycopersici, is a global threat to tomato production that needs to be addressed seriously. The current research envisages the use of two self-compatible Bacillus strains, Bacillus tequilensis PKDN31 and Bacillus licheniformis PKDL10, in a combinatorial approach. The spent supernatant of liquid cultures from strains PKDN31 and PKDL10 showed in vitro antifungal activity against Fusarium sp. attaining an inhibition percentage of 95.33% and 96.54%, respectively. The bacterial isolates lytic activity against Fusarium oxysporum was evaluated by scanning electron microscopic analysis and lytic enzyme production of amylase, lipase, protease and ß-1,3 glucanase. Furthermore, PKDN31 and PKDL10 produced siderophores and had root colonizing ability that enhanced the biocontrol efficiency. Combined in vivo inoculation of Bacillus tequilensis PKDN31 and Bacillus licheniformis PKDL10 on tomato seeds revealed that the strains could induce systemic resistance in tomato against Fusarium oxysporum. f. sp. lycopersici by increasing defence enzymes such as ß-1,3 glucanase, polyphenol oxidase, peroxidase, phenylalanine ammonia-lyase, chitinase, and total phenol accumulations. Pot culture experiments also proved the biocontrol efficacy of the above dual culture supplementation as this treatment displayed a better growth as well as defense against Fusarium challenge compared to the controls. The obtained results suggest that rhizobacterial isolates could be employed as systemic resistance inducers and biocontrol agents in tomato plants to protect against Fusarium wilt disease.

Leads and hurdles to sustainable microbial bioplastic production.

Indiscriminate usage, disposal and recalcitrance of petroleum-based plastics have led to its accumulation leaving a negative impact on the environment. Bioplastics, particularly microbial bioplastics serve as an ecologically sustainable solution to nullify the negative impacts of plastics. Microbial production of biopolymers like Polyhydroxyalkanoates, Polyhydroxybutyrates and Polylactic acid using renewable feedstocks as well as industrial wastes have gained momentum in the recent years. The current study outlays types of bioplastics, their microbial sources and applications in various fields. Scientific evidence on bioplastics has suggested a unique range of applications such as industrial, agricultural and medical applications. Though diverse microorganisms such as Alcaligenes latus, Burkholderia sacchari, Micrococcus species, Lactobacillus pentosus, Bacillus sp., Pseudomonas sp., Klebsiella sp., Rhizobium sp., Enterobacter sp., Escherichia sp., Azototobacter sp., Protomonas sp., Cupriavidus sp., Halomonas sp., Saccharomyces sp., Kluyveromyces sp., and Ralstonia sp. are known to produce bioplastics, the industrial production of bioplastics is still challenging. Thus this paper also provides deep insights on the advancements made to maximise production of bioplastics using different approaches such as metabolic engineering, rDNA technologies and multitude of cultivation strategies. Finally, the constraints to microbial bioplastic production and the future directions of research are briefed. Hence the present review emphasizes on the importance of using bioplastics as a sustainable alternative to petroleum based plastic products to diminish environmental pollution.

Biodegradation of petroleum based and bio-based plastics: approaches to increase the rate of biodegradation.

Plastic production and consumption are on the rise due to their variety of uses. Plastics often accumulate in the environment and pose a risk due to the lack of a viable strategy for their safe disposal. Even prohibiting plastic covers does not solve the problems of plastic waste generation. Plastics are degraded by various microbes, although at a very slow rate. In addition, efforts to enhance plastic degradation efficiency by microbes are rarely addressed. This paper describes the biodegradation of both petroleum-based and bio-based plastics, as well as studies on plastic biodegradation in both the Indian and global scenarios. This paper also discusses the biochemical and molecular aspects of plastic biodegradation, which are essential since they disclose more about how bacteria break down plastics. We also shed light on initiatives to boost biodegradation rates using various strategies in this article. Understanding the enzymes and genes involved in biodegradation would also help researchers figure out how to use them to enhance microorganism's ability to degrade plastic.

Chitosan nanoparticles as a rice growth promoter: evaluation of biological activity.

The agriculture sector is the building block of an economy with more than 60% of the world population depending on it for livelihood. Among the many crops, rice is the most important income source. It is the staple food for more than half of the world population. In spite of its huge demand, rice production has been dwindling due to various constraints. Chitosan nanoparticles (ChNP) are an excellent choice for agricultural applications owing to its non-toxic, biodegradable nature. Chitosan is an interesting polymer and is then partially or fully deacetylated chitin. In the present study, the effectiveness of ChNP as a growth promoter in improving the yield and biological activity of rice has been analyzed. 1 mg/ml of ChNP was applied as a seed, soil, foliar and combination treatments and the growth and yield parameters were measured to understand the best mode of application. The combination treatment of seed, soil and the foliar application was found to be most efficient. The cellular uptake of ChNP was also studied to deduce the mechanism of action. The soil toxicity of ChNP was studied prior to application and was found to be non-toxic.

Characterization of the major antifungal extrolite from rice endophyte Lysinibacillus sphaericus against Rhizoctonia solani.

Sheath blight of rice caused by Rhizoctonia solani is regarded as one of the most widely distributed diseases of rice, and is one of the major production constraints for rice in India and most rice-growing countries of Asia. Biological control of plant diseases using antagonistic bacteria is now considered as a promising alternative to the use of hazardous chemical fungicides or bactericides. Several bacterial endophytes have been reported to support growth and improve the health of the plants and therefore, may be important as biocontrol agents. In the present study, putative antifungal metabolites were extracted from rice foliage endophyte Lysinibacillus sphaericus KJ872548 by solvent extraction methods and purified using HPTLC techniques. Separated bands were subjected to assess the in vitro antagonistic activity toward rice sheath blight pathogen Rhizoctonia solani using a dual culture method. Partially purified active fraction B2 obtained from HPTLC analysis showed the highest percentage of inhibition (76.9%). GC MS and FTIR analyses of B2 revealed the compound as1, 2-Benzenedicarboxylic acid butyl 2-Ethylhexyl ester, a strong antifungal volatile organic compound. Light microscopic analysis of the fungal mycelium from the dual culture plate of both culture filtrate and 1, 2-Benzenedicarboxylic acid butyl 2-Ethylhexyl ester disclosed strong mycolytic activity as evident by mycelial distractions and shrinkage. This is the first report on antifungal production by endophytic Lysinibacillus sphaericus against R. solani, the rice sheath blight pathogen. The findings of this study biologically prospect the endophyte L. sphaericus as an inexpensive broad spectrum bioagent for eco-friendly, economic and sustainable agriculture.

Induction of defence response in Oryza sativa L. against Rhizoctonia solani (Kuhn) by chitosan nanoparticles.

Rice is a major food source for more than half of the world population. It is the only crop whose cultivation utilizes large area of land for food production. Recent surveys on rice production revealed that its potential yield has drastically reduced and its demand has exceeded over its production. In this context, the present study focuses on the biocontrol ability of chitosan nanoparticles (ChNP) against rice sheath blight pathogen (ShB) Rhizoctonia solani. To determine the percent disease suppression, detached leaf assay followed by greenhouse experiments were performed. The defence enzyme levels as well as the total phenol content were analysed to understand the mechanism of action of ChNP against ShB. This study recommends ChNP as a cost-effective alternative for chemical fungicides with potential biocontrol efficacy. ChNP was found to suppress 90% disease in detached leaf assay and 75% under greenhouse conditions. The enzyme specific activity of all the defence enzymes were significantly higher than the chemical control. The peroxidase, phenylalanine ammonia-lyase and chitinase enzymes were found to be the most active defence enzymes with 0.19,7.28 and 118.16 U/min/ml/mg protein compared to 0.01, 4.99 and 62.22 U/min/ml/mg protein for control. Hence, the current study suggest that ChNP, a non-toxic biodegradable biopolymer, can be an effective biocontrol agent against ShB caused by R.solani. It is a potent plant immunity booster that can be used as a suitable alternative to commercially available chemical fungicides. Further field trials in this respect are needed to determine the dosage for their application in rice fields.

Exploring the efficacy of antagonistic rhizobacteria as native biocontrol agents against tomato plant diseases.

As the environmental and health concerns alert the necessity to move towards a sustainable agriculture system, biological approach using indigenous plant growth-promoting rhizobacteria (PGPR) gains a strong impetus in the field of plant disease control. In this context, the present review article addresses the usage of rhizospheric antagonistic bacteria as a suitable alternative to control tomato fungal diseases namely Fusarium wilt and early blight disease. Biological control has been considered to be an eco-friendly, safe and effective method for disease management. The inherent traits of PGPR to antagonize a pathogen through various mechanisms has been investigated extensively to utilize them as potent biocontrol agents (BCA). Hence, the article provides a detailed account on different biocontrol mechanisms displayed by BCA. It is also suggested that the use of bacterial consortium ensures consistent performance by BCA in field conditions. Likewise, this review also deals with the opportunities and obstacles faced during commercialization of these antagonistic bacteria as biocontrol agents in the market.

A potential antifungal and growth-promoting bacterium Bacillus sp. KTMA4 from tomato rhizosphere.

Plant growth-promoting rhizobacteria are indigenous beneficial bacteria that will enhance plant growth as well as suppress phytopathogens. In the present study, the isolate KTMA4 showed the highest inhibition against major phytopathogens of tomato; Fusarium oxysporum (66%) and Alternaria solani (54%) after seven days of incubation. Analysis of the 16S rRNA gene sequence revealed that the isolate KTMA4 is Bacillus cereus (MG547975). The isolate produced in vitro plants growth-promoting factors such as Indole-3-acetic acid, ammonia, catalase, siderophore and 1-aminocyclopropane-1-carboxylate deaminase and it has nitrogen fixation ability. The bacterial strain has also produced lytic enzymes such as amylase, cellulase, xylanase, lipase, and protease. Moreover, the bacterium Bacillus cereus KTMA4 effectively produced biofilm, biosurfactants and salt-tolerant (5% NaCl). The bacterium exhibited intrinsic antibiotic resistance. The in vivo studies using tomato plants grown from seeds treated with the bacterial strain KTMA4 demonstrated an enhancement in seed germination percentage (86.66 ± 2.88) and vigour index (637.5 ± 21.65) over the uninoculated control (germination percentage- 28.33 ± 2.88 and vigour index- 42.5 ± 4.33). 60 days of greenhouse study revealed that the bacterial isolate enhanced the plant growth significantly (P ≤ 0.05) compared to the uninoculated control and the treated plants. Therefore the study suggests that the newly isolated rhizosphere bacterial strain can be used as a potential biocontrol agent against a multitude of fungal pathogens as well as a biofertilizer inoculant for tomato cultivation.

Chemotaxonomic profiling of Penicillium setosum using high-resolution mass spectrometry (LC-Q-ToF-MS).

In the present study, secondary metabolites produced by an endophytic fungus Penicillium setosum were extracted using colony agar plug and culture broth extraction methods. High resolution LC-MS was used to explore the chemical nature of the secondary metabolites, as well, compare the reliability of the methods. P. setosum was chemotaxonomically distinguished from other members of section Lanata-divaricata, by its ability to produce mycotoxin, patulin and also by the presence of certain phenol-derived compounds, like quercetin, dihydroflavonols (dihydroquercetin and dihydromyricetin), kaempferol, luteolin, while some Penicillium specific compounds such as, citromycetin and andrastin D reveal its similarity towards section Lanata-Divaricata members. For the first time, the presence of dihydroquercetin is remarkably and spectrometrically confirmed from a microbial source. In addition, a few polyketides, anthroquinone compounds, hydrocarbons, and fatty acids were also detected in the culture extract. Being the first report on the production of polyphenolic compounds by an endophytic fungus of Penicillium species, the current research is crucial, and moreover the starin itself is a novel species.

In vitro and in silico docking studies of antibacterial compounds derived from endophytic Penicillium setosum.

Occasionally, endophytic fungal species cognize as a hidden prospective source of plant secondary metabolites. In this study, a potent Penicillium setosum sp. nov. was explored for its detailed antibacterial action on Escherichia coli and Staphylococcus aureus through different in vitro and in silico assays. Fluorescence based viability assay determined increase in the number of dead cells in course of time with the continual exposure of extract during a 4 h period. Scanning electron micrographs reflect the distinguishable morphological changes in treated cells, namely shortening of size, bubbles, and blisters on the surface of E. coli, as well as open holes and deep craters on the surface of S. aureus, ultimately leading to rupture of cells. Significant intracellular changes in bacteria were remarkably noticed through different membrane permeabilization assays. The rate of Na+ and K+ leakage with respect to time, intracellular material and cytoplasmic ß-galactosidase release were measured spectroscopically. The results indisputably prove that membrane disruption of S. aureus cells occurs within 2 h and in E.coli occurs in between 2 and 4 h of exposure. Crude extract of P. setosum was fractioned using semi-preparative HPLC and the separated antibacterial active fraction showed antibacterial efficacy with the minimum inhibitory concentration of 8 µg/mL against both organisms. Active fraction contains four well-known plant metabolite belongs to the polyphenolic group (Leucodelphinidin, dihydroquercetin, kaempferol, and quercetin) and one polyketide (patulin) familiar as fungal metabolite, identified through high resolution LC-MS. Interaction mechanisms of identified compounds with nine important antimicrobial drug targets showed highest binding affinity by leucodelphinidin followed by dihydroquercetin > kaempferol > quercetin. This is the first instance of using leucodelphinidin and dihydroquercetin for detailed interaction study with multiple targets, and it was found that they showed more effective interaction than quercetin, which was earlier utilized for antibacterial studies.

Penicillium setosum, a new species from Withania somnifera (L.) Dunal.

Medicinal plants are considered as sources of novel and unexplored groups of endophytic microorganisms. A study on endophytic fungal species from the medicinal plant Withania somnifera (L.) Dunal resulted in the isolation of a Penicillium isolate (WSR 62) with antibiotic activity. Phylogenetic analysis showed that the isolate belongs to section Lanata-divaricata, and it is most closely related to P. javanicum. Subsequent detailed phylogenetic analyses using partial ß-tubulin (BenA), calmodulin (CaM) and DNA-dependent RNA polymerase II (RPB2) gene sequences of a larger number of related strains revealed the distinctiveness of the isolate in the P. javanicum-clade. The isolate grows fast on Czapek yeast autolysate agar (CYA) and malt extract agar (MEA) incubated at 25°C, 30°C and 37°C. The obverse colony colour is dominated by the conspicuous production of cleistothecia and is greyish yellow on CYA and yellowish brown on MEA. Production of cleistothecia containing prominent spinose ascospores was present on all tested agar media. Based on the phylogenetic analysis and the phenotypic characterisation, strain WSR 62 from Withania is described here as a novel species named Penicillium setosum.

Optimization of chitosan nanoparticle synthesis and its potential application as germination elicitor of Oryza sativa L.

The worldwide rice production has been dwindling due to biotic and abiotic causes. Chitosan is a proven biofunctional material that induces many biological responses in plants. However, the growth and yield increasing properties of chitosan nanoparticles (ChNP) on rice crop are not well understood. In the present work, effect of ChNP on germination of rice has been studied. Seed toxicity of ChNP was also analyzed to ensure the safety of ChNP application. The toxicity study was done according to EPA guidelines and ChNP was found to be non-toxic. Rice seeds were treated with ChNP at different concentrations for different time periods and kept for germination. Upon complete germination, the seedlings were sown in seed trays and growth was evaluated at 21 days after sowing. All treatments showed better results than the untreated control. Treatment T22 (1 mg/ml ChNP for 120 mins) gave the highest growth rates. Therefore we could deduce that ability of ChNP to elicit growth was associated with the concentration of ChNP and soaking time. The shelf life of ChNP was studied over a period of one year by analyzing the germination eliciting capacity on rice seeds. ChNP was found to effective for seven months when stored under room temperature.

Antifungal, antioxidant and cytotoxic activities of chitosan nanoparticles and its use as an edible coating on vegetables.

Chitosan is an abundant non-toxic, biodegradable polymer with versatile applications. It is a linear amino polysaccharide obtained from crustacean shells. The chitosan nanoparticles (ChNP) prepared by ionic gelation of chitosan has greater activity owing to its small size. ChNP has been proved to be effective in controlling plants diseases. In this work, we have endeavoured to study the antifungal and antioxidant activity of ChNP and use of ChNP as a vegetable coating material. The activity of ChNP against selected plant pathogens Rhizoctonia solani, Fusarium oxysporum, Collectotrichum acutatum, and Phytophthora infestans were studied along with a brief account of its mechanism of action. The antioxidant activity of ChNP was also analysed. The ability of ChNP as a coating material to improve the shelf life of tomato, chilly and brinjal was also studied. The cytotoxicity effect of ChNP against L929 fibroblast cells was studied. ChNP had good antifungal activity against all selected pathogens compared to Amphotericin B. Significant antioxidant activity was obtained. The vegetables coated with different concentrations of ChNP (1%, 2%, 3%, 4% and 5%) showed decreased weight loss compared to uncoated control. ChNP was shown to have decreased cytotoxicity thus making it an ideal antifungal, antioxidant and coating agent.

A novel three-stage bioreactor for the effective detoxification of sodium dodecyl sulphate from wastewater.

Anionic surfactants like sodium dodecyl sulphate (SDS), due to its extensive disposal to water bodies cause detrimental effects to the ecosystem. Among the various attempts to reduce the after effects of these toxicants, microbial induced bioremediation serves as a promising strategy. The current study aimed to develop a three stage bioreactor to remediate anionic surfactants in wastewater using effective bacterial isolates. Screening of effective SDS biodegraders led to isolation of Pseudomonas aeruginosa (MTCC 10311). Treatment of synthetic effluent with an immobilized packed bed reactor at a flow rate of 5 mL h-1 resulted in 81 ± 2% SDS eliminations and 70 ± 1% reduction in chemical oxygen demand (COD) in five cycles (6 h per cycle). The hydraulic retention time of the reactor was found to be 6 h. Combinatorial usage of a three stage bioreactor, involving aeration, adsorption with low cost scrap rubber granules and treatment with immobilized Pseudomonas aeruginosa, successfully reduced SDS concentrations and COD of wastewater to 99.8 ± 0.1% and 99 ± 1%, respectively, in 18 h by continuous treatment. Half-life of the three stage bioreactor was 72 h. In addition to reducing the surfactant concentrations, this novel bioreactor could resolve the surfactant associated foaming problems in treatment plants, which make it more unique.

Bioprospecting endophytic diazotrophic Lysinibacillus sphaericus as biocontrol agents of rice sheath blight disease.

The present study tried to explore the possible in vitro biocontrol mechanisms of Lysinibacillus sphaericus, a diazotrophic endophyte from rice against the rice sheath blight pathogen Rhizoctonia solani. The in vivo biocontrol potential of the isolate and the induction of systemic resistance under greenhouse conditions have also been experimented employing different treatments with positive control carbendazim, the chemical fungicide. The endophytic isolate showed 100% growth inhibition of the fungal pathogen via volatile organic compound production and was positive for the production of siderophores, biosurfactants, HCN, and ammonia. Under greenhouse conditions, foliar and soil application of L. sphaericus significantly decreased the percentage of disease incidence. All bacterized treatments are superior to chemical fungicide treatment. Application of L. sphaericus in single and combination treatments induces systemic resistance as evident from the significant accumulation of defense enzymes such as peroxides, polyphenol oxides and phenylalanine ammonia in addition to the increase of phenolic compounds. The results biologically prospect endophytic diazotroph L. sphaericus as a potent plant growth promoter with excellent biocontrol efficiency.

Biocontrol potential of Halotolerant bacterial chitinase from high yielding novel Bacillus Pumilus MCB-7 autochthonous to mangrove ecosystem.

The multifaceted role of chitinase in medicine, agriculture, environmental remediation and various other industries greatly demands the isolation of high yielding chitinase producing microorganisms with improved properties. The current study aimed to investigate the isolation, characterization and biocontrol prospective of chitinase producing bacterial strains autochthonous to the extreme conditions of mangrove ecosystems. Among the 51 bacterial isolates screened, Bacillus pumilus MCB-7 with highest chitinase production potential was identified and confirmed by 16S rDNA typing. Chitinase enzyme of MCB-7 was purified; the chitin degradation was evaluated by SEM and LC-MS. Unlike previously reported B.pumilus isolates, MCB-7 exhibited highest chitinase activity of 3.36U/mL, active even at high salt concentrations and temperature up to 60°C. The crude as well as purified enzyme showed significant antimycotic activity against agricultural pathogens such as Aspergillus flavus, Aspergillus niger, Aspergillus fumigatus, Ceratorhiza hydrophila and Fusarium oxysporum. The enzyme also exhibited biopesticidal role against larvae of Scirpophaga incertulas (Walker). [Lep.: Pyralidae], a serious agricultural pest of rice. The high chitinolytic and antimycotic potential of MCB-7 increases the prospects of the isolate as an excellent biocontrol agent. To the best of our knowledge, this is the first report of high chitinase yielding Bacillus pumilus strain from mangrove ecosystem with a biocontrol role against phytopathogenic fungi and insect larval pests.

Thermal properties of tannin extracted from Anacardium occidentale L. using TGA and FT-IR spectroscopy.

The chemical nature of the polyphenols of cashew kernel testa has been determined. Testa contains tannins, which present large molecular complexity and has an ancient use as tanning agents. The use of tannins extracted from cashew testa, considered in many places as a waste, grants an extra value to the cashew. In this work we have analysed through high performance liquid chromatography, infrared spectroscopy (FT-IR) and thermo gravimetric analysis the average molecular weight, main functional groups and thermal properties of tannins extracted from Anacardium occidentale L. The results of these analyses are compared with the commercial grade tannic acid. The FT-IR spectra showed bands characteristic of C = C, C-C and OH bonds. This important bioactive compound present in the cashew nut kernel testa was suggested as an interesting economical source of antioxidants for use in the food and nutraceutical industry.

Bioconversion of sodium dodecyl sulphate to rhamnolipids by transformed Escherichia coli DH5α cells-a novel strategy for rhamnolipid synthesis.

AIMS: Biological synthesis of rhamnolipids from SDS by Pseudomonas aeruginosa S15 is found to be a cost effective mode of rhamnolipid synthesis. This study aimed to attempt rhamnolipid synthesis by transformant Escherichia coli DH5α cells. METHODS AND RESULTS: Molecular analysis by curing experiments revealed that the properties of SDS based rhamnolipid synthesis were plasmid borne. Transformation of 10 kb plasmid to E. coli DH5α cells conferred rhamnolipid synthetic ability to transformant. Various genetic elements involved in SDS based rhamnolipid synthesis were analyzed using PCR based and restriction digestion based approaches. PCR amplification using primers specific for sdsA gene encoding alkylsulfatases yielded two significant amplicons viz, 1·2 kb fragment and 422 bp fragment, coding for putative dehydratase and ABC transporter respectively. Amplicon of sdsB gene lacked ability of SDS degradation and rhamnolipid synthesis. Rhamnolipid biosynthesis by transformant E. coli DH5α containing the whole of the 10 kb plasmid, was optimized to yield of 3·38 g l(-1) in 5 days of incubation. CONCLUSIONS: Plasmid encoded rhamnolipid synthesis from recombinant E. coli cells is novel and could serve as yet another promising approach among various steps adopted for safe and effective rhamnolipid synthesis. SIGNIFICANCE AND IMPACT OF THE STUDY: SDS based rhamnolipid synthesis by S15 attained a high substrate (SDS) to product (Rhamnolipid) conversion ratio. However, the use of Pseudomonas strains is always discouraged as they are opportunistic pathogens and could sometimes turn infectious. Thus, transformation of genetic elements coding SDS based rhamnolipid synthesis to nonpathogenic strains could be promising.

Growth enhancement of rice (Oryza sativa) by phosphate solubilizing Gluconacetobacter sp. (MTCC 8368) and Burkholderia sp. (MTCC 8369) under greenhouse conditions.

Two indigenous rhizospheric phosphate solubilizing isolates PSB 12 identified as Gluconacetobacter sp. (MTCC 8368) and PSB 73 identified as Burkholderia sp. (MTCC 8369) were examined for their growth enhancement potential of rice (Jyothi PTB 39) under pot culture assays. The results showed significant impact on microbial count and PSB population, phosphatase and dehydrogenase activity, available phosphorous in the soil, plant nutrient uptake and yield parameters. Gluconacetobacter sp. + RP60 treatment (30.96 µg PNP g-1 soil) retained highest phosphatase activity whereas Gluconacetobacter sp. + Burkholderia sp. + RP60 treatment recorded maximum dehydrogenase activity (38.88 µg TPF g-1 soil) after 60 days of treatment. The treatments Burkholderia sp. + RP60 and Gluconacetobacter sp. + RP60 produced comparable amount of P and these treatments were statistically at par throughout the growth period. Highest nutrient uptake and yield was noted in Gluconacetobacter sp. + Burkholderia sp. + RP60 treatment. A positive synergistic interaction between strains of Gluconacetobacter sp. and Burkholderia sp. has been noticed for their plant growth promotion activity. These strains could be of potential to develop as biofertilizers after testing their performance under field conditions either alone or as components of integrated nutrient management systems.