Production Of Antibacterial Substances Research Articles

Optimized Novel Antibacterial Production from Geobacillus kaustophilus Tm6T2 (a) as Treatment for Salmonella typhimurium

Geobacillus sp. is recognized for its potential to produce bacteriocins, antibacterial substances that hold promise in addressing gastrointestinal illnesses. This study aimed to optimize the medium and pH conditions for producing antibacterial substances by Geobacillus kaustophilus Tm6T2 (a). The research employed a descriptive and experimental methodology. Growth studies were conducted in Mueller Hinton Broth with CaCl2 and MgSO4 and Nutrient Broth with KCl and MgCl2 across 6, 7, and 8 pH values. Subsequently, antibacterial substance production was achieved at the late logarithmic phase and was assessed against the gastrointestinal pathogen Salmonella typhimurium. Interestingly, findings indicated that antibacterial substance production might not solely correlate with bacterial cell count. Despite a lower bacterial cell count, the highest inhibition zone against S.typhimurium was observed at 13.11 mm in NB salt at pH 8. Analytical results show that the variation of pH and both mediums significantly affects the presence of the inhibition zone (p < 0.10). This finding suggests the complexity of factors influencing antibacterial activity. Overall, the optimum condition for antibacterial production in G.kaustophilus Tm6T2(a) was identified at pH 8 using NB salt. These findings have potential implications for developing antibacterial solutions targeting gastrointestinal pathogens.

Antiparasitic Activity of Enterocin M and Durancin-like from Beneficial Enterococci in Mice Experimentally Infected with Trichinella spiralis.

Beneficial/probiotic strains protect the host from pathogens by competitive displacement and production of antibacterial substances, i.e., bacteriocins. The antiparasitic potential of bacteriocins/enterocins and their producing strains in experimental murine trichinellosis were tested as a new therapeutic strategy. Enterocin M and Durancin-like and their producers Enterococcus faecium CCM8558 and Enterococcus durans ED26E/7 were administered daily to mice that were challenged with Trichinella spiralis. Our study confirmed the antiparasitic effect of enterocins/enterococci, which reduced the number of adults in the intestine (Enterocin M-43.8%, E. faecium CCM8558-54.5%, Durancin-like-16.4%, E. durans ED26E/7-35.7%), suppressed the Trichinella reproductive capacity ex vivo (Enterocin M-61%, E. faecium CCM8558-74%, Durancin-like-38%, E. durans ED26E/7-66%), and reduced the number of muscle larvae (Enterocin M-39.6%, E. faecium CCM8558-55.7%, Durancin-like-15%, E. durans ED26E/7-36.3%). The direct effect of enterocins on Trichinella fecundity was documented by an in vitro test in which Durancin-like showed a comparable reducing effect to Enterocin M (40-60%) in contrast to the ex vivo test. The reducing activity of T.spiralis infection induced by Enterocin M was comparable to its strain E. faecium CCM8558; Durancin-like showed lower antiparasitic activity than its producer E. durans ED26E/7.

Review on application of probiotics in poultry farm

Poultry farming, raising of birds domestically or commercially, primarily for meat and eggs but also for feathers. In poultry industry, probiotics applications have widely been shown to improve the barrier function of intestine and reduce pathogenic problems in gastrointestinal tract thus leading to the enhancement of immune response and replacement of sub-therapeutic antibiotics. Probiotics, the novel feed or food supplements are naturally occurring beneficial live microbes including bacteria, fungi and yeasts. Probiotics are proven to improve the health and wellbeing of birds. As a group of growth promoters, the addition of probiotics to the diet of poultry has been found to improve growth performance, feed conversion efficiency, immune responses and help in combating enteric pathogens. The addition of probiotics to poultry diet also improves egg production in layers. Three basic mechanisms of probiotics include competitive exclusion of pathogenic microbes, production of antibacterial substances and immune modulation of host. Generally, live a pathogenic microbial strain, singly or as multistrain probiotics, belonging to genus Lactobacillus, Streptococcus, Bacillus, Enterococcus, Pediococcus, Aspergillus and Saccharomyces are used in poultry. The injudicious and prolific use of sub-therapeutic levels of antibiotics in animal feed to suppress or eliminate harmful organisms, and to improve growth and feed efficiency, have paved way for their presence as residues in animal by-products and have also given rise to drug resistant microorganisms. Because of public health concerns, nowadays, the use of probiotics as substitute for antibiotics in poultry production has become an area of great interest. The present article reviews the beneficial effects and potential applications of probiotics or direct fed microbial (DFM) on health and production performances in poultry.

Stress Hormone Adrenaline Boosts the Antibacterial Properties of L. plantarum and E. hallii

Amid intense exercise, the human body’s quick adaptability to stressful conditions is vital to cellular function, initiating what we recognize as an “adrenaline rush”. Despite findings on the in vitro interaction of adrenaline with the gut microbiome to regulate its virulence gene expression through AI-3 quorum sensing, studies conducted to examine the influence of the stress hormone adrenaline released through exercise on the function of the microbiome in our gut are yet insufficient. The human gut consists of a variety of microbes such as L. plantarum and E. hallii that hold vital roles in maintaining metabolic balance in the gut microbiome. Through our research, we envisioned investigating how adrenaline treatment at different time intervals or concentrations mirroring the various circumstances of exercise may affect bacterial growth, antibacterial substance production, and their antibacterial properties. While both bacteria were not affected in its growth for 48 hours, in L. plantarum, demonstrating decreased growth in the first 8 hours, its main functions — lactic acid production — were furthered with the hormone. In E. hallii, butyric acid production, with the hormone, significantly increased in its supernatant, and the intermediate treatment of adrenaline for 8 hours served to catalyze the rate at which the bacteria reached its stationary phase of growth. The study holds great promise for future investigations on how such a mechanism can be applied to therapies boosting our existing abilities of protein disposal directly correlated to the prevention of diseases. What remains is, nevertheless, the discussion regarding the true control center of these bacteria that interact with adrenaline to cause changes in the antibiotic properties, function, and growth. In other words, future studies can be oriented towards understanding the changes in the antibacterial properties of given bacteria not indirectly through chemicals with antibacterial traits but rather through the quantitative measurement of growth inhibition with other bacteria or organisms.

Production of antibacterial substance by immobilized cells of Geobacillus subterraneus Tm6Sp1 isolate of Mount Kamojang Crater, west java, against pathogenic bacteria

Production of antibacterial substance by immobilized cells of Geobacillus subterraneus Tm6Sp1 isolate of Mount Kamojang Crater, west java, against pathogenic bacteria

Probiotics from Dairy Products on Intestinal Barrier Function Using Caco-2 Cells under Microscope.

With the continuous improvement of human living standards, people's demand for health has become an important international research hotspot. In recent years, 41.3% of the total incidence of multiple organ failure (MOF) caused by dysfunction of the intestinal screen was found every year. The mortality rate is 62%, which is more than twice that of developed countries. This paper is aimed at observing the microscopic effects of probiotics derived from dairy products using Caco-2 cells on intestinal barrier function. Based on the above background, the purpose of this study was to construct a Caco-2 cell model under microscope to study the effect of probiotics on intestinal barrier function. This study first describes the background knowledge of the integration of modern microscope technology and medical field and the correlation between them. The results showed that the relative adhesion rates of Lactobacillus bulgaricus, Lactobacillus acidophilus, and Streptococcus thermophilus were 4.67 ± 0.07%, 11.53 ± 0.06%, and 18.31 ± 0.08%, respectively, which were lower than those in the normal group. The production of antibacterial substances can inhibit intestinal pathogens and adjust the balance of intestinal flora.

Enhanced Antibacterial Activity of Brevibacillus sp. SPR19 by Atmospheric and Room Temperature Plasma Mutagenesis (ARTP)

Antibiotic resistance is a major health concern worldwide. In our previous study, some bacterial isolates exhibited antibacterial activity against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA). However, the production of antibacterial substances by native microorganisms is limited by biosynthetic genes. This study aimed to improve the antibacterial activity of SPR19 using atmospheric and room temperature plasma mutagenesis (ARTP). The results showed that SPR19 belonged to the Brevibacillus genus. The growth curves and production kinetics of antibacterial substances were investigated. Argon-based ARTP was applied to SPR19, and the 469 mutants were preliminarily screened using agar overlay method. The remaining 25 mutants were confirmed by agar well diffusion assay against S. aureus TISTR 517 and MRSA isolates 142, 1096, and 2468. M285 exhibited the highest activity compared to the wild-type strain (10.34–13.59%) and this mutant was stable to produce the active substances throughout 15 generations consistently. The antibacterial substances from M285 were tolerant to various conditions (heat, enzyme, surfactant, and pH) while retaining more than 90% of their activities. Therefore, Brevibacillus sp. SPR19 is a potential source of antibacterial substances. ARTP mutagenesis is a powerful method for strain improvement that can be utilized to treat MRSA infection in the future.

Пробіотики та інфекційні хвороби

Стаття присвячена темі застосування пробіотиків у практиці інфекційних хвороб. Надано інформацію щодо механізмів дії пробіотиків, а саме: посилення епітеліального бар’єра, інгібування адгезії патогенних мікроорганізмів, конкурентне пригнічення росту патогенних мікроорганізмів, продукція антибактеріальних субстанцій та модуляція імунної відповіді.

Screening of New Potential Probiotics Strains against Photobacterium damselae Subsp. piscicida for Marine Aquaculture.

Simple SummaryMarine aquaculture has been one of the fastest growing animal production sectors in the last thirty years worldwide. On intensive farms, 10% of the population dies exclusively from pathogen activity, and Photobacterium damselae subsp. piscicida is one of the major infectious agents causing marine fish mortality. The purpose of this study is to obtain potential probiotic strains against pasteurellosis, in order to limit the use of chemotherapy, avoiding the environmental impact generated by the abusive use of these products. Bacterial strains isolated from different fish species were characterized in vitro and in vivo to determine their probiotic properties. Of the total number of strains isolated, only one showed excellent results to continue its characterization in vivo against this marine pathogen. The use of this strain as a possible probiotic for marine aquaculture will be in progress in future studies.On intensive fish farms, 10% of the population dies exclusively from pathogens, and Photobacterium damselae subsp. Piscicida (Ph. damselae subsp. Piscicida), the bacteria causing pasteurellosis in marine aquaculture, is one of the major pathogens involved. The objective of this study was to obtain new probiotic strains against pasteurellosis in order to limit the use of chemotherapy, avoiding the environmental repercussions generated by the abusive use of these products. In this study, 122 strains were isolated from the gills and intestines of different marine fish species and were later evaluated in vitro to demonstrate the production of antagonistic effects, the production of antibacterial substances, adhesion and growth to mucus, resistance to bile and resistance to pH gradients, as well as its harmlessness and the dynamic of expression of immune-related genes by real-time PCR after administration of the potential probiotic in the fish diet. Only 1/122 strains showed excellent results to be considered as a potential probiotic strain and continue its characterization against Ph. damselae subsp. piscicida to determine its protective effect and elucidating in future studies its use as a possible probiotic strain for marine aquaculture.

Optimization of culture conditions for antibacterial substance production from newly isolated Brevibacillus laterosporus EA62

Objectives: In the present study, it was reported the effects of some nutritional (amino acid, carbon, nitrogen and metal sources) and physical factors (pH and temperature) on antibacterial substance activity of Brevibacillus laterosporus EA62. Methods: The agar well diffusion assay was performed to evaluate the antibacterial activity of the substance. The antibacterial activity of the new substance was examined against four pathogenic bacteria under different nutritional and physical conditions. Results: The best antibacterial activity was obtained in modified medium consists of the 5% glucose, 0.1% tryptone, 0.05% MgSO4+CaCO3 and 0.5% glutamic acid. For physical parameters, maximal activity was observed after 72 h when incubated at 37°C, pH 7.0. Conclusions: This study indicates that Brevibacillus laterosporus EA62 could be an important source of antibacterial substances under this medium optimization.

Antibacterial Bioactivity of Some Lactic Acid Bacteria Isolated from Various Egyptian Products

The current research aimed to isolate and screening of antibacterial bioactive lactic acid bacteria (LAB) from different foods such as raw milk, dairy products and fermented meat and evaluate their potential for production of antibacterial substances, namely bacteriocins. Ten samples were collected from different market foods, examined and used for LAB isolation on MRS medium. A total of 71 bacterial isolates were selected based on some variation properties, such as color, shape, size and oxygen requirements. These isolates were confirmed as lactic acid bacteria based on their microscopic observation and chemical properties, i.e. catalase negative and acid producing from glucose fermentation. All selected isolates were grown on MRS medium at 37oC for 48 h, and compared to identified LAB strains, i.e. Lactococcus lactis, Streptococcus thermophilus, Befidobacterium sp, Lactobacillus casi, Lb rhamnosus, Lb. acidophilus, Lb. helveticus and Lb. plantarum. Isolates and strains were surveyed for bacteriocin production as inhibitory activity test. Partial purification of bacteriocin was carried out by salt precipitation method; this method was done by ammonium sulphate 40-60% saturation and centrifuged at 9500 rpm for 20 minutes at 4oC. Some of microbial indicator strains found to test by inhibitory biological activity substance (partial purification of bacteriocin) produced by lactic acid cultures. Indicator strains such as staphylococcus aureus, Listeria monocytogenes and others were grown by nutrient agar at 37o C for 24h. An inhibitory activity test was executed by paper diffusion method. The inhibition effect was examined by form clear inhibition zone around indicator strains. Twenty-eight isolates and the 8 LAB strains showed bioactivities against the tested pathogens. Gram positive indicator bacteria were found to be the most sensitive to inhibitory substances produced by LAB culture as compared to gram negative indicator strains. Staphylococcus aureus was exhibited the highest sensitivity to it. The highest bacteriocins activities were produced by strain Lactobacillus rhamnosus while R5 and S6 from LAB isolates. They were shown broad spectrum against gram positive and gram-negative pathogenic bacteria. Diameters of inhibition zone refer to degree of sensitive between indicator strains and bacteriocin activity

SUCUKTAN İZOLE EDİLEN PEDIOCOCCUS SUŞLARININ BAZI TEKNOLOJİK ÖZELLİKLERİNİN BELİRLENMESİ

Bu çalışmanın amacı, sucuktan izole edilen Pediococcus acidilactici (31 adet) ve Pediococcus pentasaceus (2 adet) suşlarının starter kültür olarak kullanım potansiyellerinin belirlenmesidir. Bu amaçla Pediococcus suşlarında laktik asit üretimi, proteolitik aktivite, lipolitik aktivite, nitrat redüktaz aktivitesi ve antibakteriyel madde üretim yetenekleri araştırılmıştır. Üç farklı besiyerinde (skim milk besiyeri, glukoz içeren skim milk besiyeri ve MRS broth besiyeri) 6. saat ve 24. saat sonunda yapılan pH ölçümleri kıyaslandığında en yüksek ΔpH değeri MRS broth besiyerinde 24 saat sonunda 1.71-2.49 aralığında hesaplanmıştır. En yüksek laktik asit üretimi de yine MRS broth besiyerinde 24 saat sonunda % 0.83-1.62 aralığında bulunmuştur. Suşların hiçbiri besiyeri ortamlarında proteolitik ve lipolitik aktivite göstermemiştir. Yirmi iki Pediococcus suşu kuvvetli, 4’ü ise zayıf nitrat redüktaz aktivitesi göstermiştir. Ayrıca tüm Pediococcus suşlarının indikatör bakterileri inhibe ettiği saptanmıştır. Sonuç olarak, hızlı asit üreten, nitrat redüktaz ve antibakteriyel aktiviteye sahip olduğu belirlenen Pediococcus suşlarının fermente et ürünleri üretiminde starter kültür olarak kullanılabileceği tespit edilmiştir.

EVALUATION OF LACTOBACILLI PROPERTIES AND THEIR ANTIBACTERIAL SUBSTANCES BY USING SWEET WHEY AS GROWTH MEDIUM AGAINST PATHOGENIC BACTERIA

The increasing demand of consumers who look for natural safe products and associated health risks of chemically treated and refined goods food products led to the introduction of alternative technologies for Preservation and maintenance of dietary freshness. One of such Preservation technology requires the use of Lactobacilli as starter culture for the preservation of food matrixes planned. The present study was designed to evaluate sweet whey low-cost by- product of dairy manufacture as a substrate for the selection of Lactobacilli with proven antibacterial activity to be used as biopreservation for fermented dairy product. Human population has used dairy products, including milk, as a source for Lactic acid bacteria (LAB). The positive impact of the given bacteria as a diet supplement has been of concern to researchers. The target of this study is to examine Lactobacillus species isolated from dairy products i.e. raw milk alongside cheese, with potential activities. Using the Sweet whey as growth medium for Lactic acid bacteria. Also, tested of antibacterial activities. Sweet whey (sw) proved to be suitable medium alternative to the expensive commercial De Man-Regosa-Sharp medium for the growth and production of antibacterial substances by isolated lactic acid bacteria isolates. Therefore, was used throughout the present work. A number of 32 isolates were obtained from raw cow milk (16 isolates), goat milk (9 isolates) and cottage cheese (7 isolates) using the specific De Man-RegosaSharp medium (MRS) for the isolation of LAB, these isolates were identified up to genus as strains of Lactobacillus spp. Among 32 isolates of Lactobacillus spp., there are twenty four isolates antagonized of the all seven tested pathogenic bacteria. The screened Lactobacillus spp. isolates were characterized and selected the best bio agent isolate against pathogens was identified using 16s DNA gene to Lactobacillus brevis. This strain was resistant to NaCl (2-6.5 %), produces dioxide carbon (CO2) and showed good growth in different temperature (10°, 15, 45°C) and fermented of many sugars. As per the outcomes shown herein, the strain in question was thought to be antimicrobial bacterium produced a variety of metabolites, including butyric, formic, lactic, citric, and sorbic acid. The given set of activities adds to microbiological safety by helping control microorganism growth, and inhibiting pathogenic bacteria by using the lower-cost sweet whey. Therefore, more detailed work on isolating and characterizing antibacterial bacteria from the locally produces dairy items, and augmenting their growth could be needed for the creation of biopreservative foods.

Evaluation of Lactobacilli properties and their antibacterial substances by using sweet whey as growth medium against pathogenic bacteria

The increasing demand of consumers who look for natural safe products and associated health risks of chemically treated and refined goods food products led to the introduction of alternative technologies for Preservation and maintenance of dietary freshness. One of such Preservation technology requires the use of Lactobacilli as starter culture for the preservation of food matrixes planned.The present study was designed to evaluate sweet whey low-cost by- product of dairy manufacture as a substrate for the selection of Lactobacilli with proven antibacterial activity to be used as biopreservation for fermented dairy product.Human population has used dairy products, including milk, as a source for Lactic acid bacteria (LAB). The positive impact of the given bacteria as a diet supplement has been of concern to researchers. The target of this study is to examine Lactobacillus species isolated from dairy products i.e. raw milk alongside cheese, with potential activities. Using the Sweet whey as growth medium for Lactic acid bacteria. Also, tested of antibacterial activities. Sweet whey (sw) proved to be suitable medium alternative to the expensive commercial De Man-Regosa-Sharp medium for the growth and production of antibacterial substances by isolated lactic acid bacteria isolates. Therefore, was used throughout the present work. A number of 32 isolates were obtained from raw cow milk (16 isolates), goat milk (9 isolates) and cottage cheese (7 isolates) using the specific De Man-Regosa-Sharp medium (MRS) for the isolation of LAB, these isolates were identified up to genus as strains of Lactobacillus spp. Among 32 isolates of Lactobacillus spp. , there are twenty four isolates antagonized of the all seven tested pathogenic bacteria. The screened Lactobacillus spp. isolates were characterized and selected the best bio agent isolate against pathogens was identified using 16s DNA gene to Lactobacillus brevis. This strain was resistant to NaCl (2-6.5 %), produces dioxide carbon (CO2) and showed good growth in different temperature (10°, 15, 45°C) and fermented of many sugars. As per the outcomes shown herein, the strain in question was thought to be antimicrobial bacterium produced a variety of metabolites, including butyric, formic, lactic, citric, and sorbic acid. The given set of activities adds to microbiological safety by helping control microorganism growth, and inhibiting pathogenic bacteria by using the lower-cost sweet whey. Therefore, more detailed work on isolating and characterizing antibacterial bacteria from the locally produces dairy items, and augmenting their growth could be needed for the creation of bio-preservative foods.

The Influencing Factors of Bacillus megaterium Affect the Growth of the Antagonistic Strain and the Activities of Antibacterial Substances

164 strains of Antagonistic bacteria were isolated from 131 mature-period soil samples from eight counties in Bijie City, Guizhou Province, China. In this study, the antagonistic bacteria that inhibited Alternaria alternata were screened and isolated. In addition, the antagonistic strain L2 was identified as Bacillus megaterium. Influencing factors also demonstrated that the suitable conditions for the production of antibacterial substances by strain L2 are as follows: liquid volume 50 mL/500 mL at pH 7.0 and 30°C under oscillation culture conditions, with beef extract as the carbon, nitrogen source.

Characterization in vitro of new bacterial strains showing potentially probiotic crossed effect against vibriosis in relevant fish species for marine aquaculture

ABSTRACT Intensive fish farms are often affected by different organisms that produce infectious diseases. To control this situation, antibiotics have been used with negative repercussions for the environment and health. As an alternative to this, probiotics are used that show more effective and respectful results with the environment. The aim of this project is to obtain new potentially probiotic strains against one of the most relevant pathogens of marine aquaculture, vibrios. These bacterial strains were isolated from the gills and intestines of European seabass, meagre and common sole. Later, were evaluated in vitro against 6 pathogenic strains of the genus Vibrio to demonstrate the production of antagonistic effects, production of antibacterial substances, resistance to bile, resistance to pH gradients, adhesion and growth to mucus, competition for nutrients and hydrophobicity. A total of 156 bacterial strains were isolated, but only 7 strains of the genera Alcaligenes, Pseudomonas, Shewanella and Proteus, showed excellent in vitro results to be considered as candidates to be reevaluated by in vivo tests, to determine their harmlessness and protective effect after challenge, and elucidating in future studies their use as possible probiotic strains for aquaculture, highlighting the results obtained with the strain Alcaligenes faecalis subsp. faecalis-1.

Characterization of Anti-Listeria monocytogenes Properties of two Bacteriocin-Producing Enterococcus mundtii Isolated from Fresh Fish and Seafood.

This study addressed the bacteriocin production in 116 lactic acid bacteria isolated from 143 fish and seafood samples. The screening for the production of antibacterial substances allowed for the selection of 16 LAB isolates endowed with inhibitory capability. Bacteriocins (bacLP17 and bacLP18) of two strains, Enterococcus mundtii LP17 and Enterococcus mundtii LP18, respectively, isolated from red mullet and sardine samples, determined large inhibition zones against all the Listeria species. Virulence traits and antibiotic resistances of all producers were verified, and no isolates presented dangerous characteristics, including the two best bacteriocin producers E. mundtii LP17 and E. mundtii LP18, which were subsequently investigated for their potential use in fish and seafood products biopreservation. For both strains, the highest level of bacteriocin production (1280AU/ml) was recorded when cells were grown at 30°C in MRS broth at pH ranging from 6.0 to 9.0, and high levels of adsorption of bacteriocins, bacLP17 and bacLP18, to the target cells Listeria monocytogenes were also observed. The results obtained in this study revealed that two strains of E. mundtii originating from seafood exhibited a strong inhibitory activity against L. monocytogenes and may be useful in controlling the growth of this pathogen in the same food products.

Characterization of a broad spectrum bacteriocin produced by Lactobacillus plantarum MXG-68 from Inner Mongolia traditional fermented koumiss.

An agar well diffusion assay (AWDA) was used to isolate a high bacteriocin-producing strain with a broad spectrum of antibacterial activity, strain MXG-68, from Inner Mongolia traditional fermented koumiss. Lactobacillus plantarum MXG-68 was identified by morphological, biochemical, and physiological characteristics and 16S rDNA analysis. The production of antibacterial substance followed a growth-interrelated model, starting at the late lag phase of 4h and arriving at a maximum value in the middle of the stationary phase at 24h. Antibacterial activity was abolished or decreased in the presence of pepsin, chymotrypsin, trypsin, proteinase, and papain K. The results showed that antibacterial substances produced by L. plantarum MXG-68 were proteinaceous and could thus be classified as the bacteriocin, named plantaricin MXG-68. The molar mass of plantaricin MXG-68 was estimated to be 6.5kDa, and the amino acid sequence of its N-terminal was determined to be VYGPAGIFNT. The mode of plantaricin MXG-68 action was determined to be bactericidal. Bacteriocin in cell-free supernatant (CFS) at pH7 was stable at different temperatures (60°C, 80°C, 100°C, 121°C for 30min; 4°C and - 20°C for 30days), as well as at pH2.0-10.0. Antibacterial activity maintained stable after treatment with organic solvents, surfactants, and detergents but increased in response to EDTA. Response surface methodology (RSM) revealed the optimum conditions of bacteriocin production in L. plantarum MXG-68, and the bacteriocin production in medium optimized by RSM was 26.10% higher than that in the basal MRS medium.

Extraction and preliminary study of antibacterial compounds of three species of Aspergillus genus

In the interest of discovering new antibiotic molecules, the antibacterial activity of three fungal strains namely: Aspergillus quadrilineatus, Aspergillus niveus, and Aspergillus wentii isolated from particular ecosystems was sought against six bacterial strains including three with Gram-positive staining (Staphylococcus aureus, Bacillus subtilis, Enterococcus faecalis) and three with Gram-negative staining (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae). The results of the agar cylinder technique highlighted that the three fungal strains showed a considerable antibacterial activity. In order to optimize the extraction conditions of the bioactive molecules, five solvents in different polarities were tested, of which chloroform turned out to be the best one. After the selection of this solvent, four culture media of different compositions were used in order to determine the most adequate medium for the production of antibacterial substances. The results revealed that Czapek-dox medium supplemented with yeast extract turned out to be the most favorable one for the production of bioactive molecules from both strains: A. quadrilineatus and A. niveus, while the most suitable medium for the A. wentii strain was Sabouraud. In addition, a study of the antibacterial effect of organic extracts by the Biolog micro-culture system was performed using a range of concentrations. The obtained results revealed that the extracts of the three fungal strains presented a remarkable activity with different concentrations and this, against all the tested bacterial strains. It was recorded only for the three used fungal species, the antibacterial activity was studied for the first time by the Biolog system.

Extraction and preliminary study of antibacterial compounds of three species of Aspergillus genus

In the interest of discovering new antibiotic molecules, the antibacterial activity of three fungal strains namely: Aspergillus quadrilineatus, Aspergillus niveus, and Aspergillus wentii isolated from particular ecosystems was sought against six bacterial strains including three with Gram-positive staining (Staphylococcus aureus, Bacillus subtilis, Enterococcus faecalis) and three with Gram-negative staining (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae). The results of the agar cylinder technique highlighted that the three fungal strains showed a considerable antibacterial activity. In order to optimize the extraction conditions of the bioactive molecules, five solvents in different polarities were tested, of which chloroform turned out to be the best one. After the selection of this solvent, four culture media of different compositions were used in order to determine the most adequate medium for the production of antibacterial substances. The results revealed that Czapek-dox medium supplemented with yeast extract turned out to be the most favorable one for the production of bioactive molecules from both strains: A. quadrilineatus and A. niveus, while the most suitable medium for the A. wentii strain was Sabouraud. In addition, a study of the antibacterial effect of organic extracts by the Biolog micro-culture system was performed using a range of concentrations. The obtained results revealed that the extracts of the three fungal strains presented a remarkable activity with different concentrations and this, against all the tested bacterial strains. It was recorded only for the three used fungal species, the antibacterial activity was studied for the first time by the Biolog system.