Enhancement of Bacillus subtilis Lipopeptide Biosurfactants Production through Optimization of Medium Composition and Adequate Control of Aeration

Interest in biosurfactants has increased considerably in recent years, as they are potentially used in many commercial applications in petroleum, pharmaceuticals, biomedical, and food processing industries. Since improvement of their production was of great importance to reduce the final coast, cultural conditions were analyzed to optimize biosurfactants production from Bacillus subtilis SPB1 strain. A high yield of biosurfactants was obtained from a culture of B. subtilis using carbohydrate substrate as a carbon source; among carbohydrates, glucose enhanced the best surfactin production. The optimum glucose concentration was 40 g/L. Higher amount of biosurfactants was obtained using 5 g/L of urea as organic nitrogen source and applying C/N ratio of 7 with ammonium chloride as inorganic nitrogen source. The highest amount of biosurfactants was recorded with the addition of 2% kerosene. Moreover, it was shown, using an automated full-controlled 2.6 L fermenter, that aeration of the medium, which affected strongly the growth regulated biosurfactants synthesis by the producing cell. So that, low or high aerations lead to a decrease of biosurfactants synthesis yields. It was found that when using dissolved oxygen saturation of the medium at 30%, biosurfactants production reached 4.92 g/L

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

Trace metals in soft tissue of marine bivalve Noah's ark (Arca noao) from Bizerte lagoon (Northern Tunisia)

peer reviewedThis study aimed to monitor the bioaccumulation of 5 trace elements (TEs: Zn, Fe, Cu, Cd, and Pb) in the soft tissue of the Ark shell (Arca noae), seasonally sampled in Bizerte lagoon, northern Tunisia, in order to assess the nutritional quality of this bivalve and to promote its consumption as marine resource in Tunisia. The levels of all trace metals analyzed in Arca noae are below maximum admissible level which makes this species a healthy and safe food for human consumption

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

Seasonal variation of biochemical composition of Noah's ark shells (Arca noae L. 1758) in a Tunisian coastal lagoon in relation to its reproductive cycle and environmental conditions

The seasonal changes in biochemical composition of the edible bivalve Arca noae harvested from a Mediterranean coastal lagoon (Bizerte lagoon, Tunisia) were investigated from October 2013 to September 2014. Potential food sources and nutritional quality indices (NQI) were determined by analyzing the fatty acid profiles of their tissues during an annual reproductive cycle. Results showed that A. noae had moisture (73.8–82%) and protein (24.1–58.6% dry weight) as major components, followed by lipid (10.4–28.8% dry weight) and glycogen (4.05–14.6% dry weight). A. noae accumulated lipid and glycogen for gonadal development during both maturation periods (late autumn/late spring–summer) to be used during spawning periods (winter/late summer–early autumn). However, proteins were mainly used to support reproductive allocation and played an important role on the energetic maintenance. Lipid and glycogen were found to be significantly related to temperature, salinity and chlorophyll a (p < 0.05). An increase of condition index (CI) was observed during spring and early summer when both temperature and food supply increased. The total fatty acid (TFA) profile of Ark shells was dominated by polyunsaturated fatty acids (PUFA) (33.8–49.6%), followed by saturated (SFA) (29.1–43.1%) and monounsaturated fatty acids (MUFA) (20.77–28.3%). A. noae soft tissues were also rich in macro-minerals (Na, Ca and Mg). The analysis of fatty acid trophic markers revealed that the diet of A. noae during the year of study was based on mixture food mainly on phytoplankton followed by zooplankton and other sources (bacteria, seagrass and macroalgae). Furthermore, the nutritional quality indices have revealed that A. noae is an excellent source of nutrients and a healthy food for human consumption. These data are useful to the conservation of natural stocks of A. noae and the development of sustainable aquaculture production of this shellfish species in the Bizerte lagoon

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

Optimization of Bacillus subtilis SPB1 Biosurfactant Production Under Solid-state Fermentation Using By-products of a Traditional Olive Mill Factory

Bacillus subtilis SPB1 is known to produce a highly effective biosurfactant that belongs to the class of lipopeptides. This biosurfactant has shown relevant properties that could be efficiently applied in various domains. However, high production and purification costs limit the use of B. subtilis SPB1 in high-volume applications. The present work aimed to promote an economical production of this lipopeptide biosurfactant. Statistical experimental designs and response surface methodology were employed to optimize the concentrations of agro-industrial residues, inoculum size and humidity for B. subtilis SPB1 biosurfactant production under solid-state fermentation. The best production yield was approximately 30.67 mg of crude lipopeptide biosurfactant per gram of solid material. This yield was obtained using a solid substrate ratio of 1.5, a moisture content of 90% and an inoculum size (OD600 ) of 0.08. These data support the utilization of a mixture of 6 g of olive leaf residue flour and 4 g of olive cake flour with a 10g total weight of the solid substrate. A mixture of two by-products of a traditional olive mill factory was demonstrated to be a suitable substrate for biosurfactant biosynthesis, providing enhanced bacterial growth and leading to a strong improvement in the yield of tensioactive lipopeptide production

Effects of increasing temperatures on biomarker responses and accumulation of trace elements in the Ark shell (Arca noae) from Bizerte lagoon

The Bizerte lagoon is one of the most studied coastal areas in Tunisia, it is used for shellfish production since 1964 and supports various industry and agriculture activities. This lagoon inhabit a wide diversity of marine invertebrates, among them the valuable shellfish Noah’s ark (Arca noae). The present study examines the influence of increasing temperature on biochemical biomarkers and metal bioaccumulation in the the total edible tissue of Arca noae. Samples were collected during winter 2013 and summer 2014 in the southern sector of the lagoon far from urban and industrial sources of pollution but this site remained influenced by agricultural inputs. After collection, Ark shells were immediately transferred to the laboratory and prepared for analysis. Five oxidative stress biomarkers: metallothioneins (MTs), malondialdehyde (MDA), glutathione peroxidase (GPx), reduced gluthatione (GSH) and acetylcholinesterase (AChE) were monitored as a response to ten trace elements bioaccumulation (Ni, Cr, Cd, Fe, Zn, Mn, Al, Cu, Se and Pb). The rise of temperature from 12°C in December to 28°C in July coincided with the bioaccumulation of trace metals, the high expression of MDA, GPx, GSH and MTs and the inhibition of AChE activity in A. noae tissues. Statistical analysis (Spearman's rank correlation) showed that all trace elements and biomarkers were significantly positively correlated with T, with the exception of Zn, Cd and AChE that was negatively correlated with this parameter. The increase of TE levels in Ark shells during summer may be due to a possible increase in the concentration of metallic elements in the lagoon waters. However, a possible contamination by runoff from adjacent farmland is to be rejected in view of the drought and the scarcity of the rains in this season. Hence, we assume that increasing concentrations of trace elements in A. noae tissues in summer is probably related to the evaporation process due to increased temperature that favors the concentration of these trace elements in the Bizerte lagoon. Thus, T (°C) appears to be a determinant factor on the variability of biomarker responses and metal bioaccumulation in A. noae. Overall, the combined effects of chemical contamination and increased temperature in summer appear to induce a highest metabolic adaptation response and can therefore be used to determine thresholds of effectiveness and facilitate the interpretation of monitoring biomarkers