Identification and characterization of a serine protease from Bacillus licheniformis W10: A potential antifungal agent

Screening and Identification of Protease-Producing Microorganisms in the Gut of Gryllotalpa orientalis (Orthoptera: Gryllotalpidae)

The insect gut harbors a diverse array of functional microorganisms that warrant further exploration and utilization. However, there is currently a paucity of research reports on the discovery of protease-producing microorganisms with industrial application value in the gut. Here, we employed microbial culturing to screen and identify the protease-producing microorganisms in the gut extract of Gryllotalpa orientalis. Based on morphological, physiological, and biochemical characterization, 16S rRNA sequencing, as well as ANI and dDDH values of whole genome, the protease-producing strains isolated from the insect gut were identified as Priestia aryahattai DBM-1 and DX-4, P. megaterium DX-3, and Serratia surfactantfaciens DBM-5. According to whole-genome analysis, strain DBM-5, which exhibited the highest enzyme activity, possesses abundant membrane transport genes and carbohydrate metabolism enzymes. In contrast, strains DX-3 and DX-4 not only have the ability to hydrolyze proteins but also demonstrate the capability to hydrolyze plant materials. Furthermore, strains that are closely related tend to have similar metabolic product gene clusters in their genomes. The screening and identification of protease resources are essential for the subsequent development and utilization of gut functional microorganisms and genetic resources in insects.

Application of liquid-based colorimetric method for high throughput screening of bioplastic-degrading strains using esterase assay

To alleviate environmental problems caused by using conventional plastics, bioplastics have garnered significant interest as alternatives to petroleum-based plastics. Despite possessing better degradability traits compared to traditional plastics, the degradation of bioplastics still demands a longer duration than initially anticipated. This necessitates the utilization of degradation strains or enzymes to enhance degradation efficiency, ensuring timely degradation. In this study, a novel screening method to identify bioplastic degraders faster was suggested to circumvent the time-consuming and laborious characteristics of solid-based plate assays. This liquid-based colorimetric method confirmed the extracellular esterase activity with p-nitrophenyl esters. It eliminated the needs to prepare plastic emulsion plates at the initial screening system, shortening the time for the overall screening process and providing more quantitative data. p-nitrophenyl hexanoate (C6) was considered the best substrate among the various p-nitrophenyl esters as substrates. The screening was performed in liquid-based 96-well plates, resulting in the discovery of a novel strain, Bacillus sp. SH09, with a similarity of 97.4% with Bacillus licheniformis. Furthermore, clear zone assays, degradation investigations, scanning electron microscopy, and gel permeation chromatography were conducted to characterize the biodegradation capabilities of the new strain, the liquid-based approach offered a swift and less labor-intensive option during the initial stages.

Exploring the frontiers of therapeutic breadth of antifungal peptides: A new avenue in antifungal drugs

The growing prevalence of fungal infections alongside rising resistance to antifungal drugs poses a significant challenge to public health safety. At the close of the 2000s, major pharmaceutical firms began to scale back on antimicrobial research due to repeated setbacks and diminished economic gains, leaving only smaller companies and research labs to pursue new antifungal solutions. Among various natural sources explored for novel antifungal compounds, antifungal peptides (AFPs) emerge as particularly promising. Despite their potential, AFPs receive less focus than their antibacterial counterparts. These peptides have been sourced extensively from nature, including plants, animals, insects, and especially bacteria and fungi. Furthermore, with advancements in recombinant biotechnology and computational biology, AFPs can also be synthesized in lab settings, facilitating peptide production. AFPs are noted for their wide-ranging efficacy, in vitro and in vivo safety, and ability to combat biofilms. They are distinguished by their high specificity, minimal toxicity to cells, and reduced likelihood of resistance development. This review aims to comprehensively cover AFPs, including their sources-both natural and synthetic-their antifungal and biofilm-fighting capabilities in laboratory and real-world settings, their action mechanisms, and the current status of AFP research.

ONE-SENTENCE SUMMARY

This comprehensive review of AFPs will be helpful for further research in antifungal research.

Biological Control of Fusarium oxysporum, the Causal Agent of Fusarium Basal Rot in Onion by Bacillus spp

Fusarium oxysporum is the main pathogen causing Fusarium basal rot in onion (Allium cepa L.), which incurs significant yield losses before and after harvest. Among management strategies, biological control is an environmentally safe and sustainable alternative to chemical control. In this study, we isolated and screened bacteria for antifungal activity against the basal rot pathogen F. oxysporum. Isolates 23-045, 23-046, 23-052, 23-055, and 23-056 significantly inhibited F. oxysporum mycelial growth and conidial germination. Isolates 23-045, 23-046, 23-052, and 23-056 suppressed the development of Fusarium basal rot in both onion seedlings and bulbs in pot and spray inoculation assays. Isolate 23-055 was effective in onion seedlings but exhibited weak inhibitory effect on onion bulbs. Based on analyses of the 16S rRNA and rpoB gene sequences together with morphological analysis, isolates 23-045, 23-046, 23-052, and 23-055 were identified as Bacillus thuringiensis, and isolate 23-056 as Bacillus toyonensis. All five bacterial isolates exhibited cellulolytic, proteolytic, and phosphate-solubilizing activity, which may contribute to their antagonistic activity against onion basal rot disease. Taken together B. thuringiensis 23-045, 23-046, 23-052, and 23-055 and B. toyonensis 23-056 have potential for the biological control of Fusarium basal rot in onion.

The Prospect of Hydrolytic Enzymes from Bacillus Species in the Biological Control of Pests and Diseases in Forest and Fruit Tree Production

Plant diseases and insect pest damage cause tremendous losses in forestry and fruit tree production. Even though chemical pesticides have been effective in the control of plant diseases and insect pests for several decades, they are increasingly becoming undesirable due to their toxic residues that affect human life, animals, and the environment, as well as the growing challenge of pesticide resistance. In this study, we review the potential of hydrolytic enzymes from Bacillus species such as chitinases, β-1,3-glucanases, proteases, lipases, amylases, and cellulases in the biological control of phytopathogens and insect pests, which could be a more sustainable alternative to chemical pesticides. This study highlights the application potential of the hydrolytic enzymes from different Bacillus sp. as effective biocontrol alternatives against phytopathogens/insect pests through the degradation of cell wall/insect cuticles, which are mainly composed of structural polysaccharides like chitins, β-glucans, glycoproteins, and lipids. This study demonstrates the prospects for applying hydrolytic enzymes from Bacillus sp. as effective biopesticides in forest and fruit tree production, their mode of biocidal activity and dual antimicrobial/insecticidal potential, which indicates a great prospect for the simultaneous biocontrol of pests/diseases. Further research should focus on optimizing the production of hydrolytic enzymes, and the antimicrobial/insecticidal synergism of different Bacillus sp. which could facilitate the simultaneous biocontrol of pests and diseases in forest and fruit tree production.

Extracellular proteases from halophiles: diversity and application challenges

Halophilic extracellular proteases offer promising application in various fields. Information on these prominent proteins including the synthesizing organisms, biochemical properties, domain organisation, purification, and application challenges has never been covered in recent reviews. Although extracellular proteases from bacteria pioneered the study of proteases in halophiles, progress is being made in proteases from halophilic archaea. Recent advances in extracellular proteases from archaea revealed that archaeal proteases are more robust and applicable. Extracellular proteases are composed of domains that determine their mechanisms of action. The intriguing domain structure of halophilic extracellular proteases consists of N-terminal domain, catalytic domain, and C-terminal extension. The role of C-terminal domains varies among different organisms. A high diversity of C-terminal domains would endow the proteases with diverse functions. With the development of genomics, culture-independent methods involving heterologous expression, affinity chromatography, and in vitro refolding are deployed with few challenges on purification and presenting novel research opportunities. Halophilic extracellular proteases have demonstrated remarkable potentials in industries such as detergent, leather, peptide synthesis, and biodegradation, with desirable properties and ability to withstand harsh industrial processes. KEY POINTS: • Halophilic extracellular proteases have robust properties suitable for applications. • A high diversity of C-terminal domains may endow proteases with diverse properties. • Novel protease extraction methods present novel application opportunities.

Biotechnological and food synthetic biology potential of platform strain: Bacillus licheniformis

Bacillus licheniformis is one of the most characteristic Gram-positive bacteria. Its unique genetic background and safety characteristics make it have important biologic applications in the food industry, including, the biosynthesis of high value-added bioproducts, probiotic functions, biological treatment of wastes derived from food production, etc. In this review, these recent advances are summarized and presented systematically for the first time. In addition, we highlight synthetic biology strategies as a potential driver of developing this strain for wider and more efficient application in the food industry. Finally, we present the current challenges faced and provide our unique perspective on relevant future research directions. In summary, this review will provide an illuminating and comprehensive perspective that will allow an in-depth understanding of B. licheniformis and promote its more effective development in the food industry.

Insights into Antifungal Mechanisms of Bacillus velezensis S141 against Cercospora Leaf Spot in Mungbean (V. radiata)

Cercospora leaf spot (CLS) is caused by Cercospora canescens and is one of the most important diseases of mungbean (Vigna radiata). Cercospora leaf spot may result in economic loss in production areas. The present study investigated the potential of Bacillus velezensis S141 as a biocontrol agent for C. canescens PAK1 growth on culture plates. Cell-free secretions from a dual culture of S141+PAK1 inhibited fungal growth more than those from a single culture of S141. The biocontrol efficiency of S141 against Cercospora leaf spot on mungbean was then evaluated by spraying. The disease severity of Cercospora leaf spot was significantly reduced in plants treated with S141, with a control efficiency of 83% after 2 days of infection. Comparative transcriptomics and qRT-PCR ana-lyses of S141 during C. canescens inhibition were performed to elucidate the antifungal mechanisms underlying its antifungal activity against Cercospora leaf spot. According to the differentially expressed genes, most up-regulated genes involved in the biosynthetic genes encoding enzymatic hydrolases, including protease, β-glucanase, and N-acyl glucosaminase, were detected in strain S141 following its interaction. Moreover, genes related to secondary metabolites (surfactin, bacilysin, and bacillomycin D) were up-regulated. Collectively, these results suggest that S141 exhibited strong antifungal activity against C. canescens due to multiple enzymatic hydrolases and secondary metabolites. Therefore, the present study provides insights into the biological network responsible for the antifungal activity of B. velezensis S141 against C. canescens.

Antifungal Activity and Possible Mechanism of Bacillus amyloliquefaciens FX2 Against the Postharvest Apple Ring Rot Pathogen

Botryosphaeria dothidea-induced apple ring rot is one of the most serious postharvest diseases in apple production. In our preliminary work, we isolated a bacterial strain (FX2) from an infested apple orchard. Here, we confirmed the strong antifungal activity of FX2 on B. dothidea. Through phylogenetic analysis and morphological observations, we identified FX2 as a Bacillus amyloliquefaciens strain. We also found that 10% cell-free supernatant (CFS) of FX2 significantly affected mycelial growth and morphology and almost completely inhibited spore germination and germ tube elongation in B. dothidea. Furthermore, 10% CFS damaged the cell ultrastructure, resulting in a remarkable increase in cellular leakage in B. dothidea mycelia. Thus, CFS has the potential to effectively reduce in vivo B. dothidea infection, reduced lesion diameters to 64.7% compared with the control group, and reduced disease incidence by 15%. Finally, ultrafiltration, desalting chromatography, and anion exchange chromatography showed that the antifungal constituents in CFS are composed mainly of antifungal proteins. We further characterized these potential antifungal proteins via liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Herein, we provide novel insights into the antifungal mechanisms of B. amyloliquefaciens FX2, and we highlight its potential as a novel biocontrol agent for controlling postharvest apple ring rot.

Bacillales: From Taxonomy to Biotechnological and Industrial Perspectives

For a long time, the genus Bacillus has been known and considered among the most applicable genera in several fields. Recent taxonomical developments resulted in the identification of more species in Bacillus-related genera, particularly in the order Bacillales (earlier heterotypic synonym: Caryophanales), with potential application for biotechnological and industrial purposes such as biofuels, bioactive agents, biopolymers, and enzymes. Therefore, a thorough understanding of the taxonomy, growth requirements and physiology, genomics, and metabolic pathways in the highly diverse bacterial order, Bacillales, will facilitate a more robust designing and sustainable production of strain lines relevant to a circular economy. This paper is focused principally on less-known genera and their potential in the order Bacillales for promising applications in the industry and addresses the taxonomical complexities of this order. Moreover, it emphasizes the biotechnological usage of some engineered strains of the order Bacillales. The elucidation of novel taxa, their metabolic pathways, and growth conditions would make it possible to drive industrial processes toward an upgraded functionality based on the microbial nature.

Broad-spectrum resistance mechanism of serine protease Sp1 in Bacillus licheniformis W10 via dual comparative transcriptome analysis

Antagonistic microorganisms are considered to be the most promising biological controls for plant disease. However, they are still not as popular as chemical pesticides due to complex environmental factors in the field. It is urgent to exploit their potential genetic characteristics and excellent properties to develop biopesticides with antimicrobial substances as the main components. Here, the serine protease Sp1 isolated from the Bacillus licheniformis W10 strain was confirmed to have a broad antifungal and antibacterial spectrum. Sp1 treatment significantly inhibited fungal vegetative growth and damaged the structure of hyphae, in accordance with that caused by W10 strain. Furthermore, Sp1 could activate the systemic resistance of peach twigs, fruits and tobacco. Dual comparative transcriptome analysis uncovered how Sp1 resisted the plant pathogenic fungus Phomopsis amygdali and the potential molecular resistance mechanisms of tobacco. In PSp1 vs. P. amygdali, RNA-seq identified 150 differentially expressed genes (DEGs) that were upregulated and 209 DEGs that were downregulated. Further analysis found that Sp1 might act on the energy supply and cell wall structure to inhibit the development of P. amygdali. In TSp1 vs. Xanthi tobacco, RNA-seq identified that 5937 DEGs were upregulated and 2929 DEGs were downregulated. DEGs were enriched in the metabolic biosynthesis pathways of secondary metabolites, plant hormone signal transduction, plant–pathogen interactions, and MAPK signaling pathway–plant and further found that the genes of salicylic acid (SA) and jasmonic acid (JA) signaling pathways were highly expressed and the contents of SA and JA increased significantly, suggesting that systemic resistance induced by Sp1 shares features of SAR and ISR. In addition, Sp1 might induce the plant defense responses of tobacco. This study provides insights into the broad-spectrum resistance molecular mechanism of Sp1, which could be used as a potential biocontrol product.

The antifungal activity of a serine protease and the enzyme production of characteristics of Bacillus licheniformis TG116

The growth of Phytophthora capsica, Rhizoctonia solani, Fusarium graminearum, Fusarium oxysporum and Botrytis cinerea were all inhibited by the fermentation supernatant of Bacillus licheniformis TG116, a biocontrol strain isolated from Typhonium giganteum Engl. previously with broad-spectrum resistance to plant pathogens. The fermentation supernatant of the TG116 has a great stability on temperature and UV, and shows the biological activity of protease and cellulase. The antifungal protease produced by B. licheniformis TG116 was purified to homogeneity by ammonium sulfate precipitation, DEAE Sepharose Fast Flow column chromatography and Sephadex G-50 column chromatography. The inhibition of protease by the three surfactants increased with increasing concentration inhibition. Among these surfactants, EDTA showed the strongest inhibition, with only 25% protein activity at a concentration of 1.1 mmol·L^-1. Gene amplification verified the presence of a gene fragment of serine protease in the strain TG116. The antimicrobial substance isolated from the fermentation broth of TG116 is a serine protease component.

Bacillus halotolerans KKD1 induces physiological, metabolic and molecular reprogramming in wheat under saline condition

Salt stress decreases plant growth and is a major threat to crop yields worldwide. The present study aimed to alleviate salt stress in plants by inoculation with halophilic plant growth-promoting rhizobacteria (PGPR) isolated from an extreme environment in the Qinghai-Tibetan Plateau. Wheat plants inoculated with Bacillus halotolerans KKD1 showed increased seedling morphological parameters and physiological indexes. The expression of wheat genes directly involved in plant growth was upregulated in the presence of KKD1, as shown by real-time quantitative PCR (RT-qPCR) analysis. The metabolism of phytohormones, such as 6-benzylaminopurine and gibberellic acid were also enhanced. Mining of the KKD1 genome corroborated its potential plant growth promotion (PGP) and biocontrol properties. Moreover, KKD1 was able to support plant growth under salt stress by inducing a stress response in wheat by modulating phytohormone levels, regulating lipid peroxidation, accumulating betaine, and excluding Na⁺. In addition, KKD1 positively affected the soil nitrogen content, soil phosphorus content and soil pH. Our findings indicated that KKD1 is a promising candidate for encouraging wheat plant growth under saline conditions.

An Evaluation of Aluminum Tolerant Pseudomonas aeruginosa A7 for In Vivo Suppression of Fusarium Wilt of Chickpea Caused by Fusarium oxysporum f. sp. ciceris and Growth Promotion of Chickpea

Chickpea wilt, caused by Fusarium oxysporum f. sp. ciceris, is a disease that decreases chickpea productivity and quality and can reduce its yield by as much as 15%. A newly isolated, moss rhizoid-associated Pseudomonas aeruginosa strain A7, demonstrated strong inhibition of Fusarium oxysporum f. sp. ciceris growth. An in vitro antimicrobial assay revealed A7 to suppress the growth of several fungal and bacterial plant pathogens by secreting secondary metabolites and by producing volatile compounds. In an in vivo pot experiment with Fusarium wilt infection in chickpea, the antagonist A7 exhibited a disease reduction by 77 ± 1.5%, and significantly reduced the disease incidence and severity indexes. Furthermore, A7 promoted chickpea growth in terms of root and shoot length and dry biomass during pot assay. The strain exhibited several traits associated with plant growth promotion, extracellular enzymatic production, and stress tolerance. Under aluminum stress conditions, in vitro growth of chickpea plants by A7 resulted in a significant increase in root length and plant biomass production. Additionally, hallmark genes for antibiotics production were identified in A7. The methanol extract of strain A7 demonstrated antimicrobial activity, leading to the identification of various antimicrobial compounds based on retention time and molecular weight. These findings strongly suggest that the strain’s significant biocontrol potential and plant growth enhancement could be a potential environmentally friendly process in agricultural crop production.

Characterization of phosphate solubilizing plant growth promoting rhizobacterium Lysinibacillus pakistanensis strain PCPSMR15 isolated from Oryza sativa

The rhizosphere soil is a source for a diversity of microorganisms which play a vital role in the enhancement of plant health through the mechanism of symbiotic interaction thereby influencing the plant growth. The present study aimed at isolating potential phosphate solubilizing rhizobacteria from rice (Oryza sativa) crop for which, four different rhizosphere soil samples were collected from different locations of Tiruvallur district, India. Isolates were cultured on nutrient agar medium followed by serial dilutions and different colonies with morphological variations were isolated from each dilution. A total of 52 bacteria were isolated and maintained as pure cultures. Out of the 52 isolates, 16 strains showed phosphate solubilizing ability and amongst them, 4 were highly potential which were subjected to morphological and biochemical characterization. Phosphate solubilizing bacterial strains when assessed for their possible effect of their inoculation on the growth and development of mung bean seeds significantly enhanced the growth of the plants. Furthermore, the potential bacteria were analysed for Indole Acetic Acid (IAA) production, which was found to be directly proportional to the plant growth promotion. Upon the comparative analysis of the four potential isolates, PCPSMR15 exhibited remarkable plant growth promoting traits. A detailed biochemical and molecular analysis identified the promising strain PCPSMR15 as Lysinibacillus pakistanensis. The present study, thus signifies the strain, PCPSMR15 for exploration as an inoculant for improving soil fertility, enhancing phosphorus availability to plants and improved crop production and sustainability.

Phytostimulation and biocontrol potential of Gram-positive endospore-forming Bacilli

The spore-forming Bacillus and Paenibacillus species represent the phyla of beneficial bacteria for application as agricultural inputs in form of effective phytostimulators, biofertilizers, and biocontrol agents. The members of the genera Bacillus and Paenibacillus isolated from several ecological habitats are been thoroughly dissected for their effective application in the development of sustainable and eco-friendly agriculture. Numerous Bacillus and Paenibacillus species are reported as plant growth-promoting bacteria influencing the health and productivity of the food crops. This review narrates the mechanisms utilized by these species to enhance bioavailability and/or facilitate the acquisition of nutrients by the host plant, modulate plant hormones, stimulate host defense and stress resistance mechanisms, exert antagonistic action against soil and airborne pathogens, and alleviate the plant health. The mechanisms employed by Bacillus and Paenibacillus are seldom mutually exclusive. The comprehensive and systematic exploration of the aforementioned mechanisms in conjunction with the field investigations may assist in the exploration and selection of an effective biofertilizer and a biocontrol agent. This review aims to gather and discuss the literature citing the applications of Bacillus and Paenibacillus in the management of sustainable agriculture.

The Role of Bacterial Proteases in Microbe and Host-microbe Interactions

BACKGROUND

Secreted proteases are an important class of factors used by bacterial to modulate their extracellular environment through the cleavage of peptides and proteins. These proteases can range from broad, general proteolytic activity to high degrees of substrate specificity. They are often involved in interactions between bacteria and other species, even across kingdoms, allowing bacteria to survive and compete within their niche. As a result, many bacterial proteases are of clinical importance. The immune system is a common target for these enzymes, and bacteria have evolved ways to use these proteases to alter immune responses for their benefit. In addition to the wide variety of human proteins that can be targeted by bacterial proteases, bacteria also use these secreted factors to disrupt competing microbes, ranging from outright antimicrobial activity to disrupting processes like biofilm formation.

OBJECTIVE

In this review, we address how bacterial proteases modulate host mechanisms of protection from infection and injury, including immune factors and cell barriers. We also discuss the contributions of bacterial proteases to microbe-microbe interactions, including antimicrobial and anti-biofilm dynamics.

CONCLUSION

Bacterial secreted proteases represent an incredibly diverse group of factors that bacteria use to shape and thrive in their microenvironment. Due to the range of activities and targets of these proteases, some have been noted for having potential as therapeutics. The vast array of bacterial proteases and their targets remains an expanding field of research, and this field has many important implications for human health.

Activity and Mechanism of Action of Antifungal Peptides from Microorganisms: A Review

Harmful fungi in nature not only cause diseases in plants, but also fungal infection and poisoning when people and animals eat food derived from crops contaminated with them. Unfortunately, such fungi are becoming increasingly more resistant to traditional synthetic antifungal drugs, which can make prevention and control work increasingly more difficult to achieve. This means they are potentially very harmful to human health and lifestyle. Antifungal peptides are natural substances produced by organisms to defend themselves against harmful fungi. As a result, they have become an important research object to help deal with harmful fungi and overcome their drug resistance. Moreover, they are expected to be developed into new therapeutic drugs against drug-resistant fungi in clinical application. This review focuses on antifungal peptides that have been isolated from bacteria, fungi, and other microorganisms to date. Their antifungal activity and factors affecting it are outlined in terms of their antibacterial spectra and effects. The toxic effects of the antifungal peptides and their common solutions are mentioned. The mechanisms of action of the antifungal peptides are described according to their action pathways. The work provides a useful reference for further clinical research and the development of safe antifungal drugs that have high efficiencies and broad application spectra.

Potential Role of Rhizobacteria Isolated from Citrus Rhizosphere for Biological Control of Citrus Dry Root Rot

Citrus trees face threats from several diseases that affect its production, in particular dry root rot (DRR). DRR is a multifactorial disease mainly attributed to Neocosmospora (Fusarium) solani and other several species of Neocosmospora and Fusarium spp. Nowadays, biological control holds a promising control strategy that showed its great potential as a reliable eco-friendly method for managing DRR disease. In the present study, antagonist rhizobacteria isolates were screened based on in vitro dual culture bioassay with N. solani. Out of 210 bacterial isolates collected from citrus rhizosphere, twenty isolates were selected and identified to the species level based on the 16S rRNA gene. Molecular identification based on 16S rRNA gene revealed nine species belonging to Bacillus, Stenotrophomonas, and Sphingobacterium genus. In addition, their possible mechanisms involved in biocontrol and plant growth promoting traits were also investigated. Results showed that pectinase, cellulose, and chitinase were produced by eighteen, sixteen, and eight bacterial isolates, respectively. All twenty isolates were able to produce amylase and protease, only four isolates produced hydrogen cyanide, fourteen isolates have solubilized tricalcium phosphate, and ten had the ability to produce indole-3-acetic acid (IAA). Surprisingly, antagonist bacteria differed substantially in their ability to produce antimicrobial substances such as bacillomycin (five isolates), iturin (ten isolates), fengycin (six isolates), surfactin (fourteen isolates), and bacteriocin (subtilosin A (six isolates)). Regarding the PGPR capabilities, an increase in the growth of the bacterial treated canola plants, used as a model plant, was observed. Interestingly, both bacterial isolates Bacillus subtilis K4-4 and GH3-8 appear to be more promising as biocontrol agents, since they completely suppressed the disease in greenhouse trials. Moreover, these antagonist bacteria could be used as bio-fertilizer for sustainable agriculture.

Biotechnological applications of Bacillus licheniformis

Bacillus licheniformis is a Gram positive spore-forming bacterial species of high biotechnological interest with numerous present and potential uses, including the production of bioactive compounds that are applied in a wide range of fields, such as aquaculture, agriculture, food, biomedicine, and pharmaceutical industries. Its use as an expression vector for the production of enzymes and other bioproducts is also gaining interest due to the availability of novel genetic manipulation tools. Furthermore, besides its widespread use as a probiotic, other biotechnological applications of B. licheniformis strains include: bioflocculation, biomineralization, biofuel production, bioremediation, and anti-biofilm activity. Although authorities have approved the use of B. licheniformis as a feed additive worldwide due to the absence of toxigenic potential, some probiotics containing this bacterium are considered unsafe due to the possible transference of antibiotic resistance genes. The wide variability in biological activities and genetic characteristics of this species makes it necessary to establish an exact protocol for describing the novel strains, in order to evaluate its biotechnological potential.

Isolation, purification, gene cloning and expression of antifungal protein from Bacillus amyloliquefaciens MG-3

The antifungal protein MG-3A was isolated from Bacillus amyloliquefaciens MG-3, and was purified and identified. The results showed that antifungal protein MG-3A was likely a serine protease with a molecular weight of ~48 kDa. The serine protease exhibited a broad antifungal spectrum and effectively extended the shelf-life of loquat fruit up to 25 d. The antifungal protein MG-3A showed good stabilities to temperature, pH and protease K. Primers were designed according to the mass spectrum of antifungal protein and the comparison with proteins in the NCBI database. The serine protease gene MG-3A from B. amyloliquefaciens genome was isolated and cloned using PCR. The prokaryotic expression plasmid pET28a-MG-3A was constructed and used to express the antimicrobial protein in vitro. The SDS-PAGE results showed that the recombinant protein expressed in Escherichia coli BL21 (DE3) was highly soluble. Affinity chromatography was used to purify the recombinant protein and its antifungal activity was evaluated.

A dual-functional aminopeptidase from Streptomyces canus T20 and its application in the preparation of small rice peptides

An aminopeptidase that derived from Streptomyces canus T20 (ScAP) was successfully expressed and characterized in Escherichia coli BL21 (DE3) for first time. The specific activity was 6000 U/mg, which is highest in Streptomyces aminopeptidases. Its optimal conditions were 60 °C and pH 8.0, respectively. ScAP exhibited excellent thermal and alkaline pH stability, retained 80.0% maximal activity at 50 °C for 200 h or at pH 9.0 for 24 h. Its activity observed to be complete inhibited by 0.1 mM EDTA and enhanced by Ca²⁺ and Co²⁺ to 115.4% and 104.0% respectively. ScAP also has exhibited high specificity towards rice protein on preparation of small peptides. The yield of small rice peptides achieved 66.5%, which is highest by far. Besides, ScAP have significant debittering effect on rice peptides. Results showed that bitter intensity score decreased by 49.0% with optimum condition (0.048% ScAP at 50 °C for 6 h). Therefore, ScAP as dual functional aminopeptidase of hydrolytic and debittering might have a potential application in the production of high yield and low bitterness of small rice peptides.

Development of nano-silver alkaline protease bio-conjugate depilating eco-benign formulation by utilizing potato peel based medium

A new bio-conjugate nano-silver enzyme conjugate complex (BC-nAg-Akp) was formulated containing alkaline protease (Akp). The present research involved synthesis of nAg particles in acetone concentrated enzyme sol using 0.005 M AgNO₃ solution formed within interaction time of 24 h through photo catalysis. The BC-nAG-Akp composite exhibited 1.9-fold increase in enzyme activity. The formulation was characterized using techniques viz., SEM, SEM-EDS, TEM, and DLS spectroscopy. The TEM analysis revealed synthesis of silver nano rods with size dimensions ranging from 40 to 80 nm. Likewise, the mean hydrodynamic diameter was 114 nm with polydispersity index of 0.260 and had the largest diffusion constant of 4.28 × 10⁸ amongst the three forms of the formulation (crude, acetone concentrated and partially purified) on DLS characterization. The SEM-EDS analysis showed occurrence of 18.32 and 3.79%weight and %atom of Ag element respectively. The prepared formulation was investigated for its dehairing performance. The ideal dehairing was achieved at 37 °C after 12 h of treatment. The histopathological studies revealed that complete dehairing with minimal rarefication was achieved and was found perform better compared to the commercial Akp and control (crude enzyme) formulations.