Production, separation, and antimicrobial activity assessment of pristinamycin produced using date fruit extract as substrate.

Date fruits extract was assessed as substrate for pristinamycin production in shake flasks using Streptomyces pristinaespiralis DSMZ 40338 as production organism. A process of microfiltration, concentration, and solvent extraction was used to recover the antibiotic from the fermentation broth and its antimicrobial activity was tested using a well assay method. During a fermentation period of 120 h, the bacterium consumed approximately 28.4 g/l sugars, grew from 0.4 g/l to 4.0 g/l dry weight, and produced 51.0 mg/L pristinamycin. The microfiltration, concentration, and ethyl acetate solvent extraction applied resulted in 71% pristinamycin recovery. The antibiotic showed inhibition capacity comparable to that of the pristinamycins IA and IIA standards. The inhibited bacteria were Staphylococcus aureus, Escherichia coli, and Enterococcus faecium. Clear inhibition zones of 13.3-19.6 mm diameter were formed.

Pristinamycin production using Streptomyces pristinaespiralis and date sirup as substrate-process modeling, optimization, and scale-up.

Pristinamycin biosynthesis using Streptomyces pristinaespiralis and date sirup (DS) as substrates was optimized before scale-up. DS was filter sterilized as heat sterilization primes Maillard reactions having negative effects on antibiotic production. Multilinear regression modeling (MLR) predicted optimum medium composition, specifying components with positive and negative effects on production. The MLR showed that to maximize bacterial growth, DS, arginine, CaCl2, and KH2PO4 must be fixed at the highest concentration, but to maximize antibiotic production, these factors have to be fixed at a low level. A noticeable difference in productivity was observed in a shake flask experiments with 50.4 and 43.1 mg/L pristinamycin final concentration for the DS and the glucose substrates, respectively. In the 2 L bioreactor, the DS medium resulted in a 66.6 mg/L antibiotic, while the scale-up in the 100 L resulted in 39.0 mg/L. The low yield in the 100 L bioreactor could be attributed to the relatively high stirring rate applied which was the minimum possible in the bioreactor used. This high stirring rate prevented pellet formation by the cells, which is described as necessary for antibiotic formation by the bacterium. Hence, a successful scale-up to pilot-scale should consider the effect of stirring rate.

Microbial contamination of date rutab collected from the markets of Al-Hofuf City in Saudi Arabia.

The microbial contamination of 60 samples from six date cultivars in the rutab stage purchased from different retail outlets in AL-Hofuf City, Saudi Arabia was studied. All samples were found contaminated with aerobic mesophilic bacteria at loads in the order 10(2) to 10(5) cfu/cm(2) with some significant differences among varieties that can be attributed to differences in the weather conditions during rutab season. Also all samples, except only one, were contaminated with molds and yeasts at loads in the order 10(2) to 10(3) cfu/cm(2). Potentially pathogenic Staphylococcus aureus was detected in 57 samples and A. flavus/parasiticus in 13 samples, while coliforms were detected in 39 samples.

Identification and safety evaluation of Bacillus species occurring in high numbers during spontaneous fermentations to produce Gergoush, a traditional Sudanese bread snack.

Gergoush is a naturally fermented Sudanese Bread snack produced in three fermentation steps (primary starter, adapted starter and final dough), followed by three baking steps for a half to one hour at above 200 °C. This study examines the microbiota of two sets of fermentations performed at a traditional production site in Khartoum, Sudan in 2006 and 2009, respectively. In 2006 four different milk/legume based primary starters (faba bean, chick pea, lentil and white bean) were sampled in order to enumerate and identify the Bacillus at species or group level. In 2009 specific focus was on the enumeration and safety evaluation of the dominant Bacillus cereus group species occurring during various Gergoush productions (including the three fermentations steps and after baking). In 2006, the primary starters contained Bacillus spp. in the order of between 7.7 and 8.1 log(10) CFU/g. Species identifications were performed by M13-PCR typing using the Escherichia coli phage M13 derived primer PM13 combined with internally transcribed 16-23S rRNA PCR, 16S rRNA gene and gyrA or gyrB gene sequencing, and selected phenotypic tests. Depending on the legume used, 40-68% of the isolates were identified as B. cereus sensu lato, 16-27% as Bacillus licheniformis, 8-32% as Bacillus subtilis and 4-20% as Bacillus sonorensis. During the second set of fermentation trials performed in 2009, the Bacillus spp. and B. cereus occurred in numbers of between 7.7-9.9 and 6.1-7.8 log(10) CFU/g, respectively, while no bacteria were detected after baking. A total of 180 B. cereus sensu lato isolates from four different primary starters, adapted starters and final doughs were further identified as B. cereus sensu stricto (118 isolates) and Bacillus thuringiensis (62 isolates). The safety of Gergoush was evaluated based on the counts and toxin gene profiles of the dominant B. cereus species. Considering that no bacteria survived the baking process, and that the cereulide synthetase gene cesB involved in the production of the heat stable emetic toxin cereulide was not detected in any of the investigated B. cereus isolates, the results indicate, that Gergoush produced at the traditional production site is safe for human consumption. This study is the first to identify the Bacillus of Gergoush to species level, and it is the first to perform a safety evaluation of the product, based on the dominant B. cereus species.