Optimization of the Nutritional Parameters for Enhanced Production of B. subtilis SPB1 Biosurfactant in Submerged Culture Using Response Surface Methodology

Nutritional requirements can contribute considerably to the production cost and the bioprocess economics. Media optimisation using response surface methodology is one of the used methods to ameliorate the bioprocess economics. In the present study, biosurfactant production by Bacillus subtilis SPB1 was effectively enhanced by response surface methodology. A Plackett-Burman-based statistical screening procedure was adopted to determine the most important factor affecting lipopeptide production. Eleven variables are screened and results show that glucose, K2HPO4, and urea concentrations influence the most biosurfactant production. A Central Composite Design was conducted to optimize the three selected factors. Statistical analyses of the data of model fitting were done by using NemrodW. Results show a maximum predicted biosurfactant concentration of 2.93 (±0.32) g/L when using 15 g/L glucose, 6 g/L urea, and 1 g/L K2HPO4. The predicted value is approximately 1.65 much higher than the original production determined by the conventional one-factor-at-a-time optimization method

Investigation of Antimicrobial Activity and Statistical Optimization of Bacillus subtilis SPB1 Biosurfactant Production in Solid-State Fermentation

During the last years, several applications of biosurfactants with medical purposes have been reported. Biosurfactants are considered relevant molecules for applications in combating many diseases. However, their use is currently extremely limited due to their high cost in relation to that of chemical surfactants. Use of inexpensive substrates can drastically decrease its production cost. Here, twelve solid substrates were screened for the production of Bacillus subtilis SPB1 biosurfactant and the maximum yield was found with millet. A Plackett-Burman design was then used to evaluate the effects of five variables (temperature, moisture, initial pH, inoculum age, and inoculum size). Statistical analyses showed that temperature, inoculum age, and moisture content had significantly positive effect on SPB1 biosurfactant production. Their values were further optimized using a central composite design and a response surface methodology. The optimal conditions of temperature, inoculum age, and moisture content obtained under the conditions of study were 37°C, 14 h, and 88%, respectively. The evaluation of the antimicrobial activity of this compound was carried out against 11 bacteria and 8 fungi. The results demonstrated that this biosurfactant exhibited an important antimicrobial activity against microorganisms with multidrug-resistant profiles. Its activity was very effective against Staphylococcus aureus, Staphylococcus xylosus, Enterococcus faecalis, Klebsiella pneumonia, and so forth

Investigation of Antimicrobial Activity and Statistical Optimization of Bacillus subtilis SPB1 Biosurfactant Production in Solid-State Fermentation

During the last years, several applications of biosurfactants with medical purposes have been reported. Biosurfactants are considered relevant molecules for applications in combating many diseases. However, their use is currently extremely limited due to their high cost in relation to that of chemical surfactants. Use of inexpensive substrates can drastically decrease its production cost. Here, twelve solid substrates were screened for the production of Bacillus subtilis SPB1 biosurfactant and the maximum yield was found with millet. A Plackett-Burman design was then used to evaluate the effects of five variables (temperature, moisture, initial pH, inoculum age, and inoculum size). Statistical analyses showed that temperature, inoculum age, and moisture content had significantly positive effect on SPB1 biosurfactant production. Their values were further optimized using a central composite design and a response surface methodology. The optimal conditions of temperature, inoculum age, and moisture content obtained under the conditions of study were 37 • C, 14 h, and 88%, respectively. The evaluation of the antimicrobial activity of this compound was carried out against 11 bacteria and 8 fungi. The results demonstrated that this biosurfactant exhibited an important antimicrobial activity against microorganisms with multidrug-resistant profiles. Its activity was very effective against Staphylococcus aureus, Staphylococcus xylosus, Enterococcus faecalis, Klebsiella pneumonia, and so forth

Association between mean platelet volume and cardiovascular disease in obstructive sleep apnea syndrome

Objectives: Obstructive sleep apnea syndrome is associated with cardiovascular diseases. Mean platelet volume has emerged as a marker of prothrombotic conditions and cardiovascular risk. The aim of this study was to investigate the association between the mean platelet volume and cardiovascular diseases in patients with obstructive sleep apnea syndrome. Methods: The medical records of 207 patients were analyzed. Obstructive sleep apnea syndrome was diagnosed by polygraphy, and patients were classified according to apnea–hypopnea index: control group: individuals with simple snoring (apnea–hypopnea index < 5), mild obstructive sleep apnea syndrome group (5 ⩽ apnea–hypopnea index < 15), moderate obstructive sleep apnea syndrome group (15 ⩽ apnea–hypopnea index < 30), and severe obstructive sleep apnea syndrome group (apnea–hypopnea index ⩾ 30). Mean platelet volume was obtained from medical records. Cardiovascular diseases were defined if patients had hypertension, heart failure, coronary artery disease, or arrythmia. The independent predictors related to cardiovascular diseases in obstructive sleep apnea syndrome were determined by using multiple logistic regression analysis. Results: Of the patients, 175 were included in the analysis. Sixty-three (36%) were males and 112 (64%) were females. The mean age was 51.85 ± 11 years. There were, 26 (14.9%), 53 (30.3%), 38 (21.7%), and 58 (33.1%) participants in the simple snoring, mild, moderate, and severe obstructive sleep apnea syndrome groups, respectively. Cardiovascular diseases were significantly different between the four groups ( p  = 0.014). Mean platelet volume in severe obstructive sleep apnea syndrome group was significantly higher than in mild or moderate obstructive sleep apnea syndrome group and simple snoring group ( p  < 0.05). Moreover, there was a positive correlation between mean platelet volume levels and apnea–hypopnea index ( r  = 0.424; p  < 0.001). The independent predictors of cardiovascular diseases in obstructive sleep apnea syndrome were age ( p  < 0.001; odds ratio = 1.134; confidence interval: 1.072–1.2), body mass index ( p  = 0.012; odds ratio: 1.105; confidence interval: 1.022–1.194), and mean platelet volume ( p  < 0.001; odds ratio: 2.092; confidence interval: 1.386–3.158). Conclusion: The present study demonstrated that there is an association between mean platelet volume levels and cardiovascular diseases in patients with obstructive sleep apnea syndrome

Metabolic capacities and toxigenic potential as key drivers of Bacillus cereus ubiquity and adaptation

Bacillus cereus is ubiquitous and commonly found in a wide range of environments,including food. In this study, we analysed 114 foodborne B. cereus strains isolated mainly from starchy and dairy products in order to investigate their phenotypic diversity (API system), antimicrobial resistance and toxigenic profiles (hblA, nheA, hlyII,cereolysin O, cytK2, cytK1 and EM1 genes). All isolates were confirmed as B. cereus using 16S-23S ribosomal DNA intergenic transcribed spacers (ITS) signature. They were shown as Gram-positive, catalase and caseinase positive, haemolytic (97%), and positive for lecithin hydrolysis and motility (97 and 87 %, respectively). PCR detection of the B. cereus specific toxin genes revealed the occurrence rates of 100 % for cereolysin O, 98 % for nheA, 74 % for cytk2, 52 % for hblA, 28 % for hlyII, and the absence of cytK1. Only two strains (1.75%), isolated from intestine of boar and pheasant, carried the emetic toxin genetic determinants (ces). Antimicrobial susceptibility of isolates was tested towards 15 different antimicrobial agents. We detected susceptibility of all strains to most antibiotics, intermediate resistance to clindamycin and resistance to β lactam antibiotics with 83% of the resistant isolates producing β lactamase enzyme. This large phenotypic diversity combined with the toxigenic traits and antibiotic resistance; emphasize the high potential risk of food poisoning of B. cereus isolates. Beside, a clear correlation between the metabolic features and the origin of isolation was shown. Most of starchy isolates were able to hydrolyse starch while dairy strains were not able to produce amylases. Our overall results point out that the metabolic flexibility and toxigenic potential represent the main drivers for B. cereus ubiquity and adaptation in a given ecological nich

Two New Secreted Proteases Generate a Casein-Derived Antimicrobial Peptide in Bacillus cereus Food Born Isolate Leading to Bacterial Competition in Milk

Milk and dairy products harbor a wide variety of bacterial species that compete for both limited resources and space. Under these competitive conditions, bacteria develop specialized mechanisms to protect themselves during niche colonization and nutrient acquisition processes. The bacterial antagonism mechanisms include the production of antimicrobial agents or molecules that facilitate competitor dispersal. In the present work, a bacterial strain designated RC6 was isolated from Ricotta and identified as Bacillus cereus. It generates antimicrobial peptide (AMP) when grown in the presence of casein. The AMP was active against several species of Bacillus and Listeria monocytogenes. MALDI-TOF analysis of the RP-HPLC purified fractions and amino acid sequencing revealed a molecular mass of 751 Da comprised of a 6-residue sequence, YPVEPF. BLAST analysis showed that the AMP corresponds to the fractions 114–119 of bovine β-casein and represents the product of a specific proteolysis. Analysis of the purified proteolytic fractions from the B. cereus RC6 culture supernatant indicated that the presence of at least two different endoproteases is crucial for the generation of the AMP. Indeed, we were able to identify two new candidate endoproteases by means of genome sequencing and functional assignment using a 3D structural model and molecular docking of misannotated hypothetical proteins. In this light, the capacity of B. cereus RC6 to generate antimicrobial peptides from casein, through the production of extracellular enzymes, presents a new model of antagonistic competition leading to niche colonization. Hence, as a dairy product contaminant, this strategy may enable proteolytic B. cereus RC6 niche specialization in milk matrices

Metabolic capacities and toxigenic potential as key drivers of Bacillus cereus ubiquity and adaptation

Bacillus cereus is ubiquitous and commonly found in a wide range of environments,including food. In this study, we analysed 114 foodborne B. cereus strains isolated mainly from starchy and dairy products in order to investigate their phenotypic diversity (API system), antimicrobial resistance and toxigenic profiles (hblA, nheA, hlyII,cereolysin O, cytK2, cytK1 and EM1 genes). All isolates were confirmed as B. cereus using 16S-23S ribosomal DNA intergenic transcribed spacers (ITS) signature. They were shown as Gram-positive, catalase and caseinase positive, haemolytic (97%), and positive for lecithin hydrolysis and motility (97 and 87 %, respectively). PCR detection of the B. cereus specific toxin genes revealed the occurrence rates of 100 % for cereolysin O, 98 % for nheA, 74 % for cytk2, 52 % for hblA, 28 % for hlyII, and the absence of cytK1. Only two strains (1.75%), isolated from intestine of boar and pheasant, carried the emetic toxin genetic determinants (ces). Antimicrobial susceptibility of isolates was tested towards 15 different antimicrobial agents. We detected susceptibility of all strains to most antibiotics, intermediate resistance to clindamycin and resistance to β lactam antibiotics with 83% of the resistant isolates producing β lactamase enzyme. This large phenotypic diversity combined with the toxigenic traits and antibiotic resistance; emphasize the high potential risk of food poisoning of B. cereus isolates. Beside, a clear correlation between the metabolic features and the origin of isolation was shown. Most of starchy isolates were able to hydrolyse starch while dairy strains were not able to produce amylases. Our overall results point out that the metabolic flexibility and toxigenic potential represent the main drivers for B. cereus ubiquity and adaptation in a given ecological nich