Chitinase Production Research Articles

Biotechnological Eminence of Chitinases: A Focus on Thermophilic Enzyme Sources, Production Strategies and Prominent Applications.

Chitin, the second most abundant polysaccharide in nature, is a constantly valuable and renewable raw material after cellulose. Due to advancement in technology, industrial interest has grown to take advantage of the chitin. Now, biomass is being treated with diverse microbial enzymes or cells for the production of desired products under best industrial conditions. Glycosidic bonds in chitin structure are degraded by chitinase enzymes, which are characterized into number of glycoside hydrolase (GHs) families. Thermophilic microorganisms are remarkable sources of industrially important thermostable enzymes, having ability to survive harsh industrial processing conditions. Thermostable chitinases have an edge over mesophilic chitinases as they can hydrolyse the substrate at relatively high temperatures and exhibit decreased viscosity, significantly reduced contamination risk, thermal and chemical stability and increased solubility. Various methods are employed to purify the enzyme and increase its yield by optimizing various parameters such as temperature, pH, agitation, and by investigating the effect of different chemicals and metal ions etc. Results: Thermostable chitinase enzymes show high specific activity at elevated temperature which distinguish them from mesophiles. Genetic engineering can be used for further improvement of natural chitinases, and unlimited potential for the production of thermophilic chitinases has been highlighted due to advancement in synthetic biological techniques. Thermostable chitinases are then used in different fields such as bioremediation, medicine, agriculture and pharmaceuticals. This review will provide information about chitinases, biotechnological potential of thermostable enzyme and the methods by which they are being produced and optimized for several industrial applications. Some of the applications of thermostable chitinases have also been briefly described.

Plant growth promoting traits of marine Micrococcus sp. with bio-control ability against Fusarium in chickpea plant

Chickpea is considered as one of the protein rich and low input crops in India but it suffers from a huge group of soil borne pathogens. Fusarium wilt, caused by Fusarium oxysporum f. sp. ciceris (FOC) at any time from the seedling to podding and become a major factor for yield loss. The aim of this study was to determine the plant growth promoting and bio-control activity of marine Micrococcus luteus and checking its in vitro effect on vegetative parameters in the presence and absence of pathogen. M. luteus was characterized as PGPB as it was tested positive for indole 3-acetic acid (IAA) production (81.379 µg ml−1 of IAA), ammonia production (1.513 µmol ml−1), potassium solubilization (17.78 µg ml−1), phosphate solubilization (81.03 ppm), glucanase production (0.5848 µmol ml−1 h−1) and chitinase production (0.024 µmol ml−1 h−1) along with antagonistic potential against four different soil borne pathogens. Talc-based bio-formulation was prepared using M. luteus and its effect on vegetative parameters was checked by performing pot trials, using four different conditions- control (T1), M. luteus treated (T2), FOC treated (T3) and both M. luteus and FOC treated (T4). M. luteus showed significantly positive effect on vegetative parameters of plants. The results suggested that M. luteus protected chickpea from pathogen as it showed bio-control ability with inhibitory effect against pathogens and act as PGPB to enhance overall plant growth.

Microbial chitinases: properties, enhancement and potential applications.

Chitinases are a category of hydrolytic enzymes that catalyze chitin and are formed by a wide variety of microorganisms. In nature, microbial chitinases are primarily responsible for chitin decomposition and play a vital role in the balance of carbon and nitrogen ratio in the ecosystem. The physicochemical attributes and the source of chitinase are the main bases that determine their functional characteristics and hydrolyzed products. Several chitinases have been reported and characterized, and they obtain a wider consideration for their utilization in a large number of uses such as in agriculture, food, environment, medicine and pharmaceutical companies. The antifungal and insecticidal impacts of several chitinases have been extensively studied, aiming to protect crops from phytopathogenic fungi and insects. Chitooligosaccharides synthesized by chitin degradation have been shown to improve human health through their antimicrobial, antioxidant, anti-inflammatory and antitumor properties. This review aims at investigating chitinase production, properties and their potential applications in various biotechnological fields.

Chitin from seafood waste: particle swarm optimization and neural network study for the improved chitinase production

AbstractBACKGROUNDThe current system in the processing of seafood leads to accumulation of many waste products, such as shells, tails, heads and bones. This seafood waste can be exploited for the extraction of chitin, with numerous applications in different fields. Seafood waste treatment can produce some valuable products. For the valorization of chitin, its degradation is an important step that can be achieved using the chitinase enzyme. Interestingly, chitin can also be used as a significant substrate for chitinase production. In this study, chitinase activity was enhanced by optimizing the fermentation medium, and chitin was used as the substrate. The polynomial model obtained by central composite design was employed in a particle swarm optimization algorithm and artificial neural network to optimize the final optimal concentration factors. The optimization results were compared for the better activity of chitinase. From the authors' best knowledge, the optimization of fermentation medium for chitinase production by particle swarm optimization was performed for the first time.RESULTSThe highest activity optimized by particle swarm optimization and artificial neural network/ Bayesian regularization algorithm) was 115.8 and 124.78 U L–1, respectively, with the optimized variables.CONCLUSIONThis study concluded that particle swarm optimization and artificial neural network are the best optimization methods for medium optimization. Among the multilayer feed‐forward algorithms in the artificial neural network, the Bayesian regularization algorithm was useful in optimizing medium components. © 2020 Society of Chemical Industry

Formulation of an exoskeleton degrading bacterial consortium from seafood processing effluent for the biocontrol of crustacean parasite Alitropus typus

Parasitic infestations on cultured fish due to the crustacean isopod Alitropus typus has been on the rise in recent years, causing large scale mortality, leading to significant economic loss to the farmer. Crustaceans are encased by an exoskeleton composed of chitin, protein and lipid microfibril frameworks, in which calcium carbonate is deposited. A strategy focused on the degradation of the exoskeletal framework utilizing nonpathogenic microorganisms that produce a wide variety of hydrolytic enzymes may be an environment-friendly and safe alternative to control these pests. The present study was aimed to formulate a microbial consortium having chitinase, protease, lipase and urease producing bacteria from seafood processing effluents that can potentially degrade the exoskeleton of A. typus. Based on the qualitative and quantitative assessment of the extracellular enzymes produced by the isolates, a novel consortium was prepared with three strains that were not antagonistic to each other and were nonpathogenic. The chitinase producing - Stenotrophomonas maltophilia and Bacillus altitudinis that produced protease and lipase as well; and non-chitinase producing Klebsiella pneumoniae were taken in the ratio of 1:1:2 respectively (109 CFU/mL). The result showed 100 % mortality of the isopods within five days when applied at a concentration of 2% (v/v) of 107 CFU/mL without any adverse effect on the fish host Oreochromis niloticus. Analysis of the ultrastructural alterations of the parasites by Environmental Scanning Electron microscopy (ESEM) showed noticeable exoskeletal damages. The microbial members of the consortium displayed remarkable chemotactic properties towards A. typus. The results suggest that the microbial consortium acts as a potential parasiticide that can be used for the control of A. typus infestation in aquaculture ponds., thus benefitting the aquaculture industry especially the small-scale farmers.

Production of Chitinase from Chromobacterium violaceum Using Agro Industrial Residues under Solid State Fermentation

Chitinases have huge potential applications and biological value in industries, they are used in generating single cell proteins, sweeteners, insecticides, antifungal drugs, anti-cancer agents, biopesticides, food processing agents, degrading agents for sea waste etc. Chitinases are used for the conversion of chitin a polysaccharide into monomers. Chitin is produced enormously in the biosphere annually from fungal cell walls, exoskeletons of insects and crustaceans. Chitinases producing microorganisms Bacillus licheniformis, Chromobacterium violaceum, Rhizobium radiobacter, Streptomyces griseous were obtained from microbial type culture collection. Solid state fermentation was done on Naturally available substrates like Fish scale waste, Prawn shell waste, Wheat bran, Potato peel, Grape leaf to check the enhanced production of Chitinase. Prawn shell waste was found to be the best natural substrate for high activity of Chitinase (464.98 U/g). The overall maximum yield of Chitinase, Chtinolytic activity (531.66 U/gds) was achieved with the optimized process parameters of incubation time(60th h), temperature(34°), inoculum age(3rd d), inoculums volume(20 % v/w), pH(7.0) moisture content 60 % v/w), 1.5 % w/w starch as Carbon source supplement and 1 % w/w urea as Nitrogen source supplement. Both physico-chemical and nutritional parameters had played a significant role in the production of the Chitinase enzyme.

Purification and Characterization of a Thermostable Chitinase Produced by a Fungus Isolated from Fruit Tree Rhizosphere

This study reveals the chitinase producing ability of some fungi isolates cultured from the rhizosphere of different fruit trees such as mango, cassava, guava, and banana inside FUTA farm. A total of 16 isolates identified as Aspergillus nidulans, A. niger, A.flavus, A. fumigatus, A. ripens, Trichoderma viride, Mucor mucedo, Penicillium frequentans, Rhizopus stolonifer, Paecilomyces fumosoroseus, Gibbelula suffulfa and Geotrichum albidum were obtained and screened for chitinolytic activity. The effect of cultural conditions such as pH, temperature, metal ion, nitrogen source and carbon source was determined on Aspergillus nidulans, being the best chitinase producer. Further, the chitinase produced by Aspergillus nidulans was concentrated by ammonium sulphate precipitation and purified consecutively by gel filtration and ion-exchange chromatography. The optimum pH and temperature for chitinase activity and stability were examined as well as the effect of metal ions on the enzyme activity. The enzyme was most active at pH 7.0 and it was relatively stable at pH 4.0 - 9.0 retaining over 60% of initial activity after 120 min of incubation. The enzyme was most active at 50°C, possessing high thermal stability at high temperature of 70°C. The purified chitinase was significantly inactivated at 80°C and almost completely at 90°C when it was pre-incubated at these temperatures for 60 min. The enzyme was strongly inhibited by FeSO4, ZnCl2 and MnCl2 and was less sensitive to CaCl2 and KCl. This purified Aspergillus nidulans chitinase can be used as a catalyst for the degradation of chitin-containing compounds.

Antagonism of plant growth promoting rhizobacteria against the causal agent of the vascular wilting of tomato

Use of biotechnological potential of native microorganisms as bio-inputs is having a great impact on agricultural systems. Plant Growth Promoting Rhizobacteria (PGPR), in addition to their beneficial effect on plant growth and on the availability of soil elements, also have an antagonistic effect against different pathogens. In this study, growth promotion mechanisms with emphasis on the antagonism of PGPR isolated from sugarcane and tomato crops were evaluated. Antagonism against Fusarium oxysporum f.sp lycopersici (Fol) was determined by dual tests, inhibition of germination and production of chitinases and endoglucanases. 52 isolates were evaluated and according to their results in dual tests 10 were selected for further analysis. Isolate GIBI127 showed the best percentage of Inhibition Germination (IG) of Fol (59.29%). Then, a selection index was calculated using results from gi, dual tests and growth promotion mechanisms to select five best isolates. Finally, these bacteria were evaluated for chitinases and endoglucanases production using Miller´s method. As a result, strain GIBI419 (Burkholderia cepacia) showed a higher production of these enzymes. Selected isolates have antagonistic potential along with plant growth promotion characteristics, which can be used for the development of microbial inoculants which allow the establishment of agricultural systems for tomato cultivation that are sustainable, efficient, and environmentally friendly.

Bacteria Isolated from the Aeration Chamber of Wastewater Treatment Plants Used in the Biocontrol and Promotion of Wheat Growth

Background: Antagonisms against Fusarium spp. and multi-traits to protect and improve fertilization of wheat by bacterial strains from activated sludge were assessed. Methods: Isolated strains obtained were identified by 16S rRNA gene sequencing and the MALDI-TOF method, and their enzymatic profile was investigated. Treated plant growth-promoting bacteria (PGPB) wheat kernels were grown in pots with soil contaminated with Fusarium conidia. Activated sludge is a collection of microorganisms exposed to strong environmental pressure (chemicals) and antagonistic properties. Results: The isolated bacterial strains were similar to: Ps-1 (Serratia liquefaciens), Ps-15 (Serratia sp.) and Ps-9 (Pseudomonas helleri). The dual culture assay showed the highest antagonism of Ps-9 vs. Fusarium spp. The tested bacteria showed activity in the production of chitinase, a variety of proteases, enzymes that degrade various sugars, and esterase, which creates a complex that allows for a variety of strategies to control phytopathogens. The Ps-9 strain was able to solubilize phosphate. The Ps-9 and Ps-15 strains showed good ammonification ability. A marked improvement was observed in test variants in pots inoculated with Fusarium spores after the use of Ps-9. The Ps-9 strain reduced the disease index to traces of symptoms of both species of Fusarium and increased the grain weight. Conclusions: The Ps-9 strain was proven to have high potential for application in the biocontrol and promotion of wheat growth.

Influence of chitinase production on the antagonistic activity of Trichoderma against plant-pathogenic fungi

Aim: The present study aimed to investigate the antagonistic activity of Trichoderma strains with high chitinase production against some plant pathogenic fungi. Methodology: A total of twenty-four Trichoderma isolates were extracted from soil samples collected at different geographical locations in Egypt and Saudi Arabia. These isolates were screened for their chitinase production ability using colloidal chitin media. Six isolates with high chitinase ability were identified as T. harzianum by internal transcribed spacer (ITS) region sequencing. These strains were tested for their ability to degrade chitin into N-acetyl-β-D-glucosaminidase. Finally, the biocontrol activities of these Trichoderma strains against pathogenic fungi were tested by dual culture technique. Results: The maximum activity among the chitinolytic enzymes was 0.051 units ml-1 in Trichoderma strain ABSA19, which showed an activity comparable to the control: pure enzyme, (0.047 units ml-1). The lowest activity (0.014 units ml-1) was found in Trichoderma strain MEG2. In dual culture, Trichoderma strain ABSA19 exerted the highest antagonistic activity in addition to hyphal intertwining and degradation using scanning electron microscopy. Finally, 11 inter simple sequence repeats (ISSR) primers were used to evaluate the genetic polymorphism among Trichoderma strains, which yielded 133 bands with fragment sizes of 130-3400 bp, 47 (35.3%) of which were polymorphic. Interpretation: The current study confirms the existence of several useful Trichoderma strains with the highest chitinase activity and antagonistic activity against some pathogenic plant fungi that may have a super potential for application in biological control of plant diseases.

Acetoine and chitinase productionby native rizobacteria from Western Paraná

The objective of this study was to investigate28 strains of nativerhizobacteriafrom the west region of Paraná, evaluating the acetoin and chitinase production capacity, because of their roleinbiocontrol. Thebacteriaisolates were submitted to the modified Voges-Proskauer (VP) assayin Clark & Lubs liquid medium forglucose fermentation. Metaboliteproductionwasevaluated in a spectrophotometer,and it showed a wide variation in concentrations (0,476to1,865) for differentisolates.Strains 241, 320, 326, and 273showedhighervaluesthan the others tested. According to positive results in the qualitative test of VP, 11 isolates were chosen for the tests in minimal medium containing chitin as the only source of carbon. Isolates that presented the degradation halo formation were considered as chitinolytic bacteria, evidencing chitinaseactivity. Among these strains, two belonged tothe genus Bacillusspp. (56 and 121) and two tothe genus Enterobacterspp. (292 and 151). Therefore, the present work was able to identify native strains with potential for biocontrol studies allowing tocontinue investigations of other metabolitesproducedby thosebacteria in this collection regarding plant protection.

FUNCTIONAL AND MOLECULAR CHARACTERIZATION OF WHEAT RHIZOSPHERE BACTERIA AND THEIR ANTAGONISTIC ACTIVITY AGAINST WHEAT FOLIAR BLIGHT PATHOGENS

The current study aimed to explore the wheat rhizospheric bacterial community for in vitro plant growth-promoting (PGP) traits and antagonistic activity against foliar blight disease of wheat caused by Alternaria triticina and Bipolaris sorokiniana. The soil samples from the wheat fields across four Indian states namely Uttarakhand (2 sites), Uttar Pradesh, Madhya Pradesh, and Maharashtra were analyzed for their physicochemical properties, enzymatic activities, and bacterial population density (CFU g-1). Amongst the tested soil samples, field soil from Uttar Pradesh has the highest bacterial population density (2.5x107 CFU g 1) while the Uttarakhand (Almora) soil has the lowest (8.5x 105 CFU g 1). A total of 45 bacterial isolates recovered from all the sites were morphologically identified and screened for in-vitro solubilization of phosphate & zinc, production of ammonia, siderophore, chitinase, protease, cellulase, amylase, lipase, and antagonistic activity. All isolates were found positive for one or more tested functional traits. Amongst 45 isolates, six showed >50% inhibition of Alternaria triticina and Bipolaris sorokiniana mycelium, and three isolates P10, UP11 & MH13 exhibited antagonistic activity against both the tested phytopathogens. Through 16S rDNA sequencing six putative biocontrol isolates, P10, UP11, MH13, MP17, MH12, and MP14 were identified as Bacillus methylotrophicus (MN099430.1), Bacillus subtilis (MN099431.1), Bacillus sp. (MN099432.1), Streptomyces sp. (MN099435.1), Lysinibacillus sp. (MN099433.1), and Staphylococcus epidermidis (MN099434.1). The selected wheat rhizobacteria exhibited PGP traits and biocontrol potential hence, may serve as putative biocontrol agents, for the management of foliar blight disease of wheat.

Protection of surplus food from fungal spoilage using Streptomyces spp.: a green approach.

Consortia of Streptomyces spp. (colonies 169, 194, 165 and 130) used in this study are an efficient producer of secondary metabolites like chitinases and antifungal compounds, which may help in the protection of surplus food from spoilage. Qualitative screening for chitinase production and taxonomy of these colonies were undertaken in our previous studies. In the current study, GC-MS analysis of extract produced from the consortia of Streptomyces strains was done for the identification of antifungal compounds. Treatment of surplus food with activated consortia of Streptomyces spp. has protected powdered food for a month, whereas fresh food (unpowdered) was preserved for two days. A control sample of surplus food (untreated) was kept to check the contamination, which resulted in the growth of three fungi (FP-1, FG-1, and FB-1). Taxonomic characterization of fungi and identification of toxic compounds produced from them were done by ITS amplification and GC-MS analysis, respectively. The study shows that the secondary metabolites from Streptomyces spp. have the potential to protect the food from mycotoxin contamination. Based on literature reports, this is for the first time that bioactive compounds and chitinases produced from Streptomyces are being used for the protection and management of surplus food.

Identification and characterization of Vietnamese coffee bacterial endophytes displaying in vitro antifungal and nematicidal activities

The endophytic bacteria were isolated from coffee roots and seeds in Vietnam and identified with 16S rDNA sequencing as belonging to the Actinobacteria, Firmicutes and Proteobacteria phyla with the Nocardia, Bacillus and Burkholderia as dominant genera, respectively. Out of the thirty genera recovered from Coffea canephora and Coffea liberica, twelve were reported for the first time in endophytic association with coffee including members of the genera Brachybacterium, Caballeronia, Kitasatospora, Lechevalieria, Leifsonia, Luteibacter, Lysinibacillus, Mycolicibacterium, Nakamurella, Paracoccus, Sinomonas and Sphingobium. A total of eighty bacterial endophytes were characterized in vitro for several plant growth promoting and biocontrol traits including: the phosphate solubilization, the indolic compounds, siderophores, HCN, esterase, lipase, gelatinase and chitinase production. A subset of fifty selected bacteria were tested for their potential as biocontrol agents with in vitro confrontations with the fungal pathogen Fusarium oxysporum as well as the coffee parasitic nematodes Radopholus duriophilus and Pratylenchus coffeae. The three most efficient isolates on F. oxysporum belonging to the Bacillus, Burkholderia, and Streptomyces genera displayed a growth inhibition rate higher than 40%. Finally, five isolates from the Bacillus genus were able to lead to 100% of mortality in 24 h on both R. duriophilus and P. coffeae.

Chitinase production by Trichoderma viride in submerged state fermentation

We have identified the optimal conditions for the production of chitinolytic enzymes of T.viride in submerged state fermentation. The production of chitinase by a new strain of fungus was carried out on the basal liquid medium, containing (%) colloidal chitin 0.5, NaNO3 0.2, KH2PO4 0.1; MgSO44-7H2O 0.05 and KCl, 0.05. The activity of enzymes of the chitinase complex of the strain was evaluated using the method using dinitrosalicylic acid (DNS reagent). A quantitative determination of the activity of chitinases in a producer microorganism was established by their ability to hydrolyze 0.2% colloidal chitin (in phosphate buffer 0.05 M, pH 5.2), by the content of reducing sugars formed in this process, which were evaluated using a DNS reagent. The results of studies of the influence of various cultivation parameters showed that highest chitinolotic enzymes production by T.viride was obtained at pH 4.0, (301.15-303.15) K and after 144 h growth. The studied soil isolate can be further used in biotechnological research, as well as for biological control of pests and pathogens of agricultural crops.

The Role of Cell Wall Degrading Enzymes in Antagonistic Traits of Trichoderma virens Against Rhizoctonia solani.

Background: High antagonistic ability of different Trichoderma species against a diverse range of plant pathogenic fungi has led them to be used as a biological fungicide in agriculture. They can also promote plant growth, fertility, resistance to stress, and absorption of nutrients. They are also opportunistic and symbiotic pathogens, which can lead to the activation of plant defense mechanisms.Objectives: The aim of this present study was to investigate possible enhancement of lytic enzymes production and biocontrol activity of T. virens against Rhizoctonia solani through gamma radiation and to find the relationship between changes in lytic enzyme production and antagonistic activity of T. virens.Material and Methods: Dual culture conditions were used to evaluate the antagonistic effect of T. virens and its gamma mutants against R. solani. Then, their chitinase and cellulase activities were measured. For more detailed investigation of enzymes, densitometry pattern of the proteins was extracted from the T. virens wild-type and its mutants were obtained via SDS-polyacrylamide gel electrophoresis.Results: The mutant T.vi M8, T. virens wild-type and mutant T.vi M20 strains showed the maximum antagonistic effects against the pathogen, respectively. Data showed that the mutant T. vi M8 reduced the growth of R. solani by 58 %. The mutants revealed significantly different (p<0.05) protein contents, chitinase and cellulase production (mg.mL-1) and activity (U.mL-1) compared to the wild-type strain. The highest extracellular protein production in the supernatant of chitinase and cellulase TFM was observed for the T.vi M11 and T.vi M17 strains, respectively. The T.vi M12 and wild-type strains secreted chitinase and cellulase significantly more than other strains did. Densitometry of SDS-PAGE gel bands indicated that both the amount and diversity of chitinase related proteins in the selected mutant (T. vi M8) were far higher than those of the wild-type. The diversity of molecular weight of proteins extracted from the T. virens M8 (20 proteins or bands) was very high compared to the wild-type (10 proteins) and mutant T.vi M15 (2 proteins).Conclusions: Overall, there was a strong link between the diversity of various chitinase proteins and the antagonistic properties of the mutant M8.

CHITINASE PRODUCTION BY ASPERGILLUS TERREUS FROM MARINE WASTES AND ITS EFFICACY IN ANTIFUNGAL ACTIVITY

The present investigation aims to isolate and identify chitinase producing mycoflora and the chitinase production by efficient Aspergillus terreus on different shell powder wastes substrates such as prawn, crab and molluscs at an extracellular and intracellular level and its efficacy in assessing the antifungal activity. Shell fish wastes disposed soil samples were collected and screened for chitinolytic fungi (hydrolyzing zone). The chitinase production on different substrates was assessed and the enzyme extracts were screened for antifungal activity by agar well and disc diffusion methods. Among the number of mycoflora isolated only 4 fungal strains Aspergillus terreus, A. fumigatus, A. flavus, and A. clavatus showed maximum hydrolyzing zones. A significantly highest hydrolyzing zone (clearance zone) of 20 mm (out of colony diameter of 65 mm) was obtained by Aspergillus terreus. Among the different substrates (prawn, crab and molluscs shell powders at 1% concentration), highest chitinase activity was recorded by Aspergillus terreus on prawn shell powder waste followed by crab shell powder waste at an intra and extra cellular level. The chitinase produced from prawn shell powder waste as substrates by A. terreus showed maximum zone of inhibition in both agar well (28.0 mm) and disc diffusion (24.0 mm) methods against the pathogenic fungi, A. flavus compared to positive control (Fluconazole). The chitinase produced from A. terreus might have synthesized some antifungal compounds which may be responsible for killing pathogenic fungi.

Multiple strategies to improve the yield of chitinase a from Bacillus licheniformis in Pichia pastoris to obtain plant growth enhancer and GlcNAc

Chitinase and chitin-oligosaccaride can be used in multiple field, so it is important to develop a high-yield chitinase producing strain. Here, a recombinant Pichia pastoris with 4 copies of ChiA gene from Bacillus licheniformis and co-expression of molecular chaperon HAC1 was constructed. The amount of recombinant ChiA in the supernatant of high-cell-density fermentation reaches a maximum of 12.7 mg/mL, which is 24-fold higher than that reported in the previous study. The recombinant ChiA can hydrolyze 30% collodidal chitin with 74% conversion ratio, and GlcNAc is the most abundant hydrolysis product, followed by N, N′-diacetylchitobiose. Combined with BsNagZ, the hydrolysate of ChiA can be further transformed into GlcNAc with 88% conversion ratio. Additionally, the hydrolysate of ChiA can obviously accelerate the germination growth of rice and wheat, increasing the seedling height and root length by at least 1.6 folds within 10 days.

Fusarium wilt biocontrol and tomato growth stimulation, using endophytic bacteria naturally associated with Solanum sodomaeum and S. bonariense plants

BackgroundFusarium wilt biocontrol using endophytic microorganisms may represent a potentially attractive and environmentally safe alternative since endophytes could better limit disease incidence and severity through inhibition of the systemic fungus progress.Main body of the abstractTwenty-three endophytic bacterial isolates, naturally associated with Solanum sodomaeum and Solanum bonariense, were evaluated for their ability to control Fusarium wilt of tomato induced by Fusarium oxysporum f. sp. lycopersici (FOL) and to promote plant growth. Selected endophytic isolates were screened in vivo, using the root dipping and the culture substrate drenching methods. The most bioactive isolates were subjected to morphological and biochemical characterization and subsequent identification through 16S rDNA sequencing genes. Seven isolates (Stenotrophomonas maltophilia S23, S24, S26 and S28; Bacillus sp. SV81; Azotobacter chroococcum S11; and Serratia marcescens S14) were found to be the most efficient in reducing disease severity by 82–96% over control. Treatments with these isolates led to a significant enhancement in growth parameters, estimated at 45.5–61 and 24.2–70.5% than the control, in tomato plants infected or not with FOL, respectively. Diffusible and volatile metabolites released from bacterial cultures had significantly limited FOL radial growth. All isolates were positive for indole-3-acetic acid (IAA) production. S. marcescens S14, S. maltophilia S28, and Bacillus sp. SV81 exhibited a positive phosphate solubilization activity. Production of chitinase, protease, pectinase, and hydrogen cyanide were also investigated.Short conclusionThis study clearly demonstrated that endophytic bacteria recovered from these 2 Solanum species can be explored as promising biocontrol agents active against FOL and are able to enhance tomato growth.

Effect of kitasamycin and nitrofurantoin at subinhibitory concentrations on quorum sensing regulated traits of Chromobacterium violaceum.

Quorum sensing (QS) is a mechanism of intercellular communication in bacteria that received substantial attention as alternate strategy for combating bacterial resistance and the development of new anti-infective agents. The present investigation reports on the assessment of using subinhibitory concentrations of antibiotics for the inhibition of QS-regulated phenotypes in Chromobacterium violaceum. Primarily, the minimum inhibitory concentrations of a series of antibiotics were determined by a microdilution method. Subsequently, the inhibitory effects of selected antibiotics on QS-regulated traits, namely violacein and chitinase production, biofilm formation and motility were evaluated using C. violaceum CV026 and C. violaceum ATCC 12472. Results revealed that kitasamycin and nitrofurantoin exhibited the highest quorum sensing inhibitory (QSI) activity. The amount of violacein produced by C. violaceum was significantly reduced in the presence of either kitasamycin or nitrofurantoin. Moreover, the chitinolytic activity, biofilm formation, and motility were also impaired in kitasamycin or nitrofurantoin-treated cultures. We further confirmed QSI effects at the molecular level using molecular docking and real-time quantitative polymerase chain reaction (RT-qPCR). Results of molecular docking suggested that both antibiotics can interact with CviR transcriptional regulator of C. violaceum. Furthermore, RT-qPCR revealed the suppressive effect of kitasamycin and nitrofurantoin on five genes under the control of the CviI/CviR system: cviI, cviR, vioB, vioC, and vioD. Giving that kitasamycin and nitrofurantoin are being safely used for decades, this study emphasizes their potential application as antivirulence agents to disarm resistant bacterial strains, making their removal an easier task for the immune system or for another antibacterial agent.