Performance of Bacillus subtilis on fibrous biomass sugar hydrolysates in producing biosurfactants and techno-economic comparison.

Surfactin and fatty acetyl glutamate (FA-Glu) were produced by Bacillus subtilis in 5-L fermentor. In a previous 50-mL shake flask study, sugar hydrolysates from soy hull, alfalfa and switchgrass were shown to support the growth of Bacillus strains. It was observed that glucose content and availability of hexose and pentose sugars in the hydrolysates played an important role in determining growth and product concentration. Growth, economic efficiency and product concentration of biosurfactants was compared in fermentations conducted in 5-L stirred tank bioreactor, on biomass hydrolysate-based growth media. Highest bacterial growth absorbance for surfactin and FA-Glu producing strains were at 3.5 and 3.3 absorbance units, respectively, for switchgrass hydrolysate media. Highest concentrations of products were observed in soy hull hydrolysate media (2.9 g/L and 0.28 g/L for surfactin and FA-Glu). Techno-economic analysis of the 5-L fermentations on the three biomasses showed surfactin cost estimate to be $6.63/kg for 97% pure product.

Evaluation of Alternaria mycotoxins in strawberries: quantification and storage condition.

Alternariol (AOH), alternariol methyl ether (AME) and tentoxin (TEN) are Alternaria mycotoxins produced by the most common post-harvest pathogens of fruits. The production of these metabolites depends on several environmental factors, mainly temperature, water activity, pH and the technological treatments that have been applied to the product. In this study, the occurrence of AOH, AME and TEN was evaluated in strawberries samples stored at different temperatures ranges (at 22 ± 2 or 6 ± 2°C) and different periods (up to 1 month) simulating the current practice of consumer's storage conditions. Sample extraction was performed using a liquid-liquid extraction method prior to LC-MS/MS analysis. AOH was the most prevalent mycotoxins with a 42% at strawberries stored at (22 ± 2)°C and 37% stored at (6 ± 2)°C. The highest AOH levels were found in samples conserved at (22 ± 2)°C ranging between 26 and 752 ng g(-1). AME levels ranged between 11 and 137 ng g(-)(1), which were found mainly in stored samples at (6 ± 2)°C for more than 28 days. None sample presented levels of TEN in either of the studied conditions.

Improvement of surfactin production in Bacillus subtilis using synthetic wastewater by overexpression of specific extracellular signaling peptides, comX and phrC.

Surfactin is a biological surfactant with numerous potential applications. In this study, Bacillus subtilis was engineered to improve surfactin production by the activation of two competence-stimulating pheromones, ComX and competence and sporulation factor (CSF) to stimulate the transcription of srfA operon. Both signaling factors, encoded by comX and phrC, were successfully overexpressed and subsequently increased surfactin production. Surfactin produced by engineered strains showed functional groups similar to the commercially available surfactin analyzed via Fourier transform infrared spectroscopy (FTIR). Surfactin production in the B. subtilis (pHT43-comXphrC) strain was 6.4-fold greater than in the wild strain, with approximately 135.1 mg/L surfactin produced after 48 h cultivation. To reduce the production costs of surfactin, synthetic wastewater was used, from which the B. subtilis (pHT43-comXphrC) strain produced approximately 140.2 mg/L surfactin. The results obtained demonstrated the production of surfactin from synthetic wastewater, which is beneficial in lowering the overall production costs.

Cytotoxicity in Bacillus mojavensis is abolished following loss of surfactin synthesis: implications for assessment of toxicity and food poisoning potential.

Bacillus subtilis and the closely related species Bacillus pumilus and Bacillus licheniformis have periodically been suggested to play a role in the aetiology of food poisoning despite the fact that the organisms do not possess the genes associated with enteropathogenicity in Bacillus cereus. We show here that Bacillus mojavensis, an organism closely related to B. subtilis, is able to produce toxic components which identify as a complex of three different surfactin analogues. These cyclic lipopeptides were soluble in methanol, heat stable after treatment in a boiling water bath for 10 min, resistant to enzymatic degradation by pepsin, trypsin, endoprotease V8 and proteinase K and formed pores in planar lipid bilayers. They were cytotoxic when tested in a series of commonly used laboratory cytotoxicity assays, namely, lactate dehydrogenase release, haemolysis, inhibition of both protein synthesis in Vero cells and motility in boar sperm. We show that such in vitro markers of enterotoxicity are due entirely to production of cyclic lipopeptides since deletion of sfp, a gene essential for surfactin synthesis which abolished the cytotoxicity to Vero cells, boar sperm motility and haemolytic activity. Thus, the relevance of cyclic lipopeptides as food poisoning toxins needs to be evaluated in assays other than the cell cytotoxicity assays in common use.