β-galactosidase from <em>Lactobacillus delbrueckii </em>and <em>Lactobacillus </em><em>reuteri</em>: Optimization, characterization and formation of galactooligosaccharides

407-415Beta-galactosidase (β-gal) is one of the important commercial enzymes having several applications in food, pharmaceutical industry and in the synthesis of galactooligosaccharides known for their prebiotic properties. The production of β-gal from Lactobacillus delbrueckii and Lactobacillus reuteri was studied. The highest yield of β-gal was achieved using wheat flour as carbon source. Beef extract gave the highest value of enzymatic production by L. delbrueckii reached 24.25 U/ml, while L. reuteri produced the highest β-gal (20.20 U/ml) in the presence of peptone. The optimum β-gal activity was recorded on 15 mM O-nitrophenyl β-D-galactopyranoside (ONPG) at 40oC and pH 7. Further enzyme activity was enhanced in the presence of Mg2+, Mn2+and Fe2+, while it was decreased by Ag+ and Ni+ for both strains. The production of galactooligosaccharides (GalOS) from lactose using the produced β-gal was investigated. The maximum yield of 40 and 35% (w/w) GalOS could be achieved with β-gal of L. delbrueckii and L. reuteri, respectively from 40% lactose solution at 40°C and pH 7. These characteristics of produced β-gal showed that it could be a promising candidate for various industrial as well as biotechnological applications

Antimicrobial, antioxidant and antitumor activities of silver nanoparticles synthesized by Allium cepa extract: A green approach

An economic and efficient method for the synthesis of silver nanoparticles (AgNPs) was performed using onion (Allium cepa) extract as reducing and capping agent. UV–vis spectroscopy confirmed the formation of silver nanoparticles by observing the typical surface plasmon resonance peak at 420 nm. Transmission electron microscopy studies revealed that AgNPs were spherical in shape with a size range of 10–23 nm. AgNPs were further demonstrated by the characteristic peaks observed in the XRD image. The possible functional groups of AgNPs were identified by FTIR analysis. AgNPs exhibited potential antimicrobial activity against all the microbial strains tested. Antioxidant activity of AgNPs revealed that they can be used as potential radical scavenger against deleterious damages caused by the free radicals. Additionally, AgNPs had antitumor activities against human breast (MCF-7), hepatocellular (HepG-2) and colon (HCT-116) carcinoma cell lines in a dose-dependent manner with IC50 of 1.6, 2.3 and 2.2 μg/ml, respectively. The overall results indicate promising baseline information for the potential uses of AgNPs in the treatment of infectious diseases and tumors

Antimicrobial activity of a biosurfactant produced by Bacillus licheniformis strain M104 grown on whey

The aim of the present study was to investigate the antimicrobial effect of the lipopeptide biosurfactants produced by Bacillus licheniformis strain M104 grown on whey. The biosurfactant was investigated for potential antimicrobial activity by using the disc-diffusion method against different Gram-positive bacteria {B subtilis, B. thuringiensis (two strains), B. cereus, Staphylococcus aureus (two strains) and Listeria monocytogenes)}, Gram-negative bacteria {(Pseudomonas aeruginosa, Escherichia coli (two strains), Salmonella typhimurium, Proteous vulgaris and Klebsiella pneumoniae) and a yeast (Candida albicans)}. The biosurfactant showed profoundly distinct antibacterial activity toward tested bacteria and displayed an antifungal activity against the tested yeast. Maximum antimicrobial activity of the biosurfactant was shown against S. aureus ATCC 25928. The biosurfactant had a broad inhibition effect on intracellular components of S. aureus ATCC 25928. The antimicrobial effect of lipopeptide biosurfactant produced by B. licheniformis strain M104 was time and concentration dependent. When biosurfactant was added to S. aureus medium in a concentration of (48 &#956;g / ml), the maximum reduction of acid soluble phosphorous (53.06 %), total lipid (90.47 %) total proteins (53.43%), RNA (83.29 %) and DNA (48.50%) were recorded after 12 h of incubation period. From the preliminary characterization results, it could be concluded that biosurfactants were a suitable alternative in potential applications of medical fields

Production of polyhydroxyalkanoates (PHAs) by Bacillus subtilis and Escherichia coli grown on cane molasses fortified with ethanol

The aim of this work was to study the production of polyhydroxyalkanoates (PHAs) by Bacillus subtilis and Escherichia coli isolated from the industrial contaminated soil samples using cane molasses as an inexpensive substrate. The amount of PHA accumulated followed a similar pattern to its growth for each of treatment indicating a growth-related production, yielding maximum PHA production of 54.1 and 47.16% for B. subtilis and E. coli, respectively after 96 h cultivation in the medium containing 6 and 8 % molasses, respectively and decreased thereafter. The growth and PHA yields were improved by introducing 1% ethanol into the molasses medium. Ammonium sulphate and ammonium nitrate at a concentration of 1 g/L served as the best nitrogen sources for bacterial growth, allowing B. subtilis and E. coli cells to accumulate PHA up to 62.21 and 58.7%, respectively. The optimum environmental conditions that influenced the PHA production by the two strains were inoculum concentration of 8%, pH 7.0 and a temperature of 35°C. The functional groups of the extracted PHA granules were identified by Fourier transform infrared (FTIR) spectroscopy analysis

Statistical Modelling and Optimization of Fermentation Medium for Lincomycin Production by Streptomyces lincolnensis Immobilized Cells

ABSTRACT Response surface methodology was used to optimize lincomycin production by Streptomyces lincolnensis NRRL ISP-5355 in submerged fermentation. Screening of fermentation medium components to find their relative effect on lincomycin production was done using Plackett-Burman design. Malt extract, dextrin, soluble starch and (NH4)2SO4 were the most significant nutrient influenced on lincomycin production. Central composite design was applied to determine optimal concentrations of these factors and the effect of their mutual interactions. The interaction between soluble starch and (NH4)2SO4 was found to enhance the production, whereas malt extract and dextrin exhibited an influence independent from the other two factors. Using this statistical optimization method, maximum lincomycin concentration of 1345 μg/ml was obtained which represented a 40.5 % increase in titer than that acquired from the non-optimized medium. This statistically optimized medium was employed for lincomycin production through immobilization of Streptomyces lincolnensis by adsorption on synthetic cotton fibers. Immobilization technique improved the concentration to 1350 μg/ml higher than that produced from free cells cultures and could be maintained for longer than 17 days in a repeated batch system