An antifungal protease produced by Pseudomonas aeruginosa M-1001 with shrimp and crab shell powder as a carbon source

Optimization of protease production by Bacillus cereus HMRSC30 for simultaneous extraction of chitin from shrimp shell with value-added recovered products

Chitin extraction from shrimp shell powder (SSP) using protease-producing microbes is an attractive approach for valorizing shrimp shell waste because it is simple and environmentally friendly. In this study, the protease production and chitin extraction from SSP by Bacillus cereus HMRSC30 were simultaneously optimized using statistical approaches. As a result, fermentation in medium composed of 30 g/L SSP, 0.2 g/L MgSO₄ · 7H₂O, 3 g/L (NH₄)₂SO₄, 0.5 g/L K₂HPO₄, and 1.5 g/L KH₂PO₄ (pH 6.5) for 7 days maximized protease production (197.75 ± 0.33 U/mL) to approximately 1.64-fold compared to unoptimized condition (126.8 ± 0.047 U/mL). This level of enzyme production was enough to achieve 97.42 ± 0.28% deproteinization (DP) but low demineralization (DM) of 53.76 ± 0.21%. The high DM of 90% could be easily accomplished with the post-treatment using 0.4 M HCl and acetic acid. In addition, the study evaluated the possible roadmap to maximize the value of generated products and obtain additional profits from this microbial process. The observation showed the possibility of serving crude chitin as a bio-adsorbent with the highest removal capacity against Coomassie brilliant blue (97.99%), followed by methylene blue (74.42%). The recovered protease exhibited the function to remove egg yolk stain, indicating its potential for use as a detergent in de-staining. The results corroborated the benefits of microbial fermentation by B. cereus HMRSC30 as green process for comprehensive utilization of shrimp shell waste as well as minimizing waste generation along the established process.

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.

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

Bacillus licheniformis W10 is a strain of biocontrol bacteria that was obtained from plant rhizosphere screening. In this study, we purified, identified, and carried out bioinformatics analysis of the W10 antifungal protein from Bacillus licheniformis. Mass spectrometry analysis was carried out by passing the antifungal protein through a high-resolution time-of-flight mass spectrometer. Mascot searches of the tandem mass spectrometry data identified this antifungal protein as a serine protease, and the 1347 bp gene encoding this protein was cloned. Bioinformatics analysis of this protein indicated that it contains 448 amino acid residues, has a molecular weight of 48,794.16 Da and an isoelectric point of 6.04, and is a hydrophilic protein. In the secondary and tertiary structure of this protein, the proportion of α-helices and β-folds is similar, and the protein possesses a Peptidase_S8 conserved domain. Using BApNA as a substrate, it was found that the serine protease inhibitor phenylmethylsulfonyl fluoride (PMSF) can inhibit the W10 antifungal protein. PMSF concurrently reduced the inhibitory effects of the antifungal protein on Botrytis cinerea, showing that the W10 antifungal protein possesses serine protease activity. The W10 antifungal protein has good thermal stability. The study implies potential of this enzyme for biocontrol of fungal plant pathogens.

Biocontrol of Orchid-pathogenic Mold, Phytophthora palmivora, by Antifungal Proteins from Pseudomonas aeruginosa RS1

Black rot disease in orchids is caused by the water mold Phytophthora palmivora. To gain better biocontrol performance, several factors affecting growth and antifungal substance production by Pseudomonas aeruginosa RS1 were verified. These factors include type and pH of media, temperature, and time for antifungal production. The results showed that the best conditions for P. aeruginosa RS1 to produce the active compounds was cultivating the bacteria in Luria-Bertani medium at pH 7.0 for 21 h at 37 °C. The culture filtrate was subjected to stepwise ammonium sulfate precipitation. The precipitated proteins from the 40% to 80% fraction showed antifungal activity and were further purified by column chromatography. The eluted proteins from fractions 9-10 and 33-34 had the highest antifungal activity at about 75% and 82% inhibition, respectively. SDS-PAGE revealed that the 9-10 fraction contained mixed proteins with molecular weights of 54 kDa, 32 kDa, and 20 kDa, while the 33-34 fraction contained mixed proteins with molecular weights of 40 kDa, 32 kDa, and 29 kDa. Each band of the proteins was analyzed by LC/MS to identify the protein. The result from Spectrum Modeler indicated that these proteins were closed similarly to three groups of the following proteins; catalase, chitin binding protein, and protease. Morphological study under scanning electron microscopy demonstrated that the partially purified proteins from P. aeruginosa RS1 caused abnormal growth and hypha elongation in P. palmivora. The bacteria and/or these proteins may be useful for controlling black rot disease caused by P. palmivora in orchid orchards.

Mycolytic enzymes produced by Streptomyces violaceusniger and their role in antagonism towards wood-rotting fungi

Extracellular mycolytic enzymes produced under submerged fermentation by the fungal antagonist Streptomyces violaceusniger MTCC 3959 were characterized. This streptomycete produced higher amounts of extracellular chitinase and protease during late exponential phase, whereas β-1,3-glucanase production was at peak in mid-stationary phase. Cell-free culture filtrate (CCF) exhibited a broad range of antifungal activity against both white rot and brown rot fungi. The inhibitory activity was completely lost after treatment with proteinase K and heat, indicating that extracellular antifungal metabolites are heat labile and proteinaceous in nature. Optimum pH and temperature for enzyme activity were: 9.0 and 60 °C for chitinase; 6.0 and 60 °C for β-1,3-glucanase; and 9.0 and 70 °C for protease. Mycolytic enzymes were moderately thermostable, and had a wide pH stability range extending from pH 5.0 to 10.0. The zymogram analysis of CCF revealed five chitinase isoenzymes with an apparent molecular weight of 20.8, 33.3, 45.6, 67.4, and 114.8 kDa, one β-1,3-glucanase appeared as a single band of ∼131.8 kDa and four protease isoenzymes with approximate molecular weights of 22.8, 62.52, 74.64, and 120.5 kDa. S. violaceusniger MTCC 3959 produced mycolytic enzymes that can be effectively used for suppression of phytopathogenic basidiomycetes. It has the potential to be an effective biofungicide.

Isolation and partial characterization of an antifungal protein produced by Bacillus licheniformis BS-3

An antifungal protein produced by Bacillus licheniformis strain BS-3 was purified to homogeneity by ammonium sulfate precipitation, DEAE-52 column chromatography and Sephadex G-75 column chromatography. The purified protein was designated as F2 protein, inhibited the growth of Aspergillus niger, Magnaporthe oryzae and Rhizoctonia solani. F2 protein was a monomer with approximately molecular weight of 31 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gave a single peak on High Performance Liquid Chromatography (HPLC). Using Rhizoctonia solani as the indicator strain, the EC₅₀ of F2 protein was 35.82 µg/mL, displaying a higher antifungal activity in a range of pH 6.0 to pH 10.0, and at a temperature below 70 °C for 30 min. F2 protein was moderately resistant to hydrolysis by trypsin, proteinase K, after which its relative activities were 41.7% and 59.5%, respectively. F2 protein was assayed using various substrates to determine the enzymatic activities, the results showed the hydrolyzing activity on casein, however, no enzymatic activities on colloidal chitin, CM-cellulose, xylan, M. lysodeikticus, and p-nitrophenyl-N-acetylglucosaminide.

Immobilization of subtilisin on polycaprolactam for antimicrobial food packaging applications

Subtilisin was immobilized on polycaprolactam and used for food packaging applications to reduce the transference of microorganisms from the packaging material to the packaged food material. The optimized conditions for subtilisin immobilization was as follows: pH, 8; temperature, 4 °C; glutaraldehyde, 0.5%; incubation time, 25 h; and subtilisin concentration, 600 μL. The formation of -CH═N- at 1576 cm(-1) in the Fourier transform infrared (FTIR) spectrum confirmed the immobilization. Subtilisin-immobilized polycaprolactam (SIP) exhibited the highest residual activity of 106.67 ± 4.41% and 104.67 ± 0.88% at 40 °C and pH 8 and retained residual activity of 94% at the end of 56 days when compared to 21.33 ± 4.10% in the case of free subtilisin. SIP significantly (p < 0.05) lowered the colony forming units (CFU), dry weight, and protein and carbohydrate contents in bacterial and fungal biofilm. Practical application of the SIP on ham steaks at 4 and 20 °C showed a 2-3 times reduction of Staphylococcus aureus as well as Escherichia coli cells in the range of p < 0.05.

A novel antifungal Pseudomonas fluorescens isolated from potato soils in Greenland

A rhizobacterium with high antifungal activity was isolated from a potato field at Inneruulalik, South Greenland. Phylogenetic analysis based on multi locus sequence typing showed that the bacterium was affiliated with strains of Pseudomonas fluorescens. The bacterium, denoted as Pseudomonas fluorescens In5, inhibited in vitro a broad range of phytopathogenic fungi, and the antifungal activity increased with decreasing temperature. Microcosm experiments demonstrated that P. fluorescens In5 protected tomato seedlings from Rhizoctonia solani. Transposon mutagenesis showed that the major cause for the antifungal activity of P. fluorescens In5 was a novel non-ribosomal peptide synthase (NRPS) gene. In addition, transposon mutagenesis showed that P. fluorescens In5 also contained a putative quinoprotein glucose dehydrogenase gene, which was involved in growth inhibition of phytopathogenic fungi. Although P. fluorescens In5 contained the capacity to synthesize hydrogen cyanide, β-1,3-glucanase, protease, and chitinase, these did not seem to play a role in the in vitro and microcosm antifungal assays.

Antifungal and Anticancer Activities of a Protein from the Mushroom Cordyceps militaris

The mushroom Cordyceps militaris has been used for a long time in eastern Asia as a nutraceutical and in traditional Chinese medicine as a treatment for cancer patients. In the present study, a cytotoxic antifungal protease was purified from the dried fruiting bodies of C. militaris using anion-exchange chromatography on a DEAE-Sepharose column. Electrophoretic analyses indicated that this protein, designated C. militaris protein (CMP), has a molecular mass of 12 kDa and a pI of 5.1. The optimum conditions for protease activity were a temperature of 37 and pH of 7.0~9.0. The enzyme activity was specifically inhibited by the serine protease inhibitor phenylmethylsulfonyl fluoride. Amino acid composition of intact CMP and amino acid sequences of three major peptides from a tryptic digest of CMP were determined. CMP exerted strong antifungal effect against the growth of the fungus Fusarium oxysporum, and exhibited cytotoxicity against human breast and bladder cancer cells. These results indicate that C. militaris represents a source of a novel protein that might be applied in diverse biological and medicinal applications.

An alkaline protease from fresh fruiting bodies of the edible mushroom Pleurotus citrinopileatus

A protease was purified from fresh fruiting bodies of the edible mushroom Pleurotus citrinopileatus. The isolation procedure included ion exchange chromatography on DEAE-cellulose, CM-cellulose, and Q-Sepharose and fast protein liquid chromatography-gel filtration on Superdex 75. The protease was unadsorbed on DEAE-cellulose and Q-Sepharose, but adsorbed on CM-cellulose. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the protease demonstrated a single band with a molecular mass of 28 kDa. The protease showed an optimal pH at 10 and an optimal temperature at 50 degrees C. The activity of the protease was not affected by EDTA, indicating that it is not a metalloprotease. The protease exhibited a higher activity in the presence of K(+) and Li(+), but its activity was potently inhibited by Al(3+), Cu(2+), and Hg(2+) ions. It manifested a K (m) of 3.44 mg/ml and a V (max) of 0.139 mg ml(-1) min(-1). It was devoid of ribonuclease and antifungal activities.