Structure-Function and Industrial Relevance of Bacterial Aminopeptidase P

Aminopeptidase P (APPro, E.C 3.4.11.9) cleaves N-terminal amino acids from peptides and proteins where the penultimate residue is proline. This metal-ion-dependent enzyme shares a similar fold, catalytic mechanism, and substrate specificity with methionine aminopeptidase and prolidase. It adopts a canonical pita bread fold that serves as a structural basis for the metal-dependent catalysis and assembles as a tetramer in crystals. Similar to other metalloaminopeptidase, APPro requires metal ions for its maximal enzymatic activity, with manganese being the most preferred cation. Microbial aminopeptidase possesses unique characteristics compared with aminopeptidase from other sources, making it a great industrial enzyme for various applications. This review provides a summary of recent progress in the study of the structure and function of aminopeptidase P and describes its various applications in different industries as well as its significance in the environment.

Microbiological and Proximate Analyses of Lebanese Bread (Pita) from Akure Metropolis

Aim: This study aimed at evaluating the microbial quality and proximate composition of pita samples from Akure metropolis. Place and Duration of Study: Microbiology and Industrial Chemistry laboratories of the Federal University of Technology, Akure (FUTA), Ondo State, Nigeria, between January 2016 and June 2016. Methodology: Pita samples were evaluated using standard microbiological techniques to ascertain microbial load and types after purchase from vendors utilizing them alone or in production of other foods. Antibiotic susceptibility profile of isolates was also determined. Proximate composition analysis of samples was also performed. Results: Average bacterial count was 1.0±0.9 cfu/g, while average fungal count was 2.0±1.2 sfu/g. The fungi isolated were Rhizopus stolonifer, Saccharomyces cerevisiae and Aspergillus niger; while the bacteria isolated were Bacillus cereus, Staphylococcus sp., Micrococcus luteus, Pseudomonas aeruginosa, and Proteus vulgaris. Microbial zones of inhibition ranged from 17 mm to 23.50 mm. Micrococcus luteus, Staphylococcus aureus and Pseudomonas aeruginosa were most susceptible to gentamycin, pefloxacin and amoxycillin, respectively. Staphylococcus aureus showed the widest antimicrobial resistant pattern. The highest carbohydrate content was recorded as 78.99 %, while bread samples showed low ash content (0.65 %). Conclusion: Pita bread is not a common staple compared to leavened breads but provides appreciable level of nutrients. Pita bread requires regular microbial assessment to determine their safety for direct consumption or use in production of other food products.

Development of a Bioactive Sauce Based on Oriental Mustard Flour with Antifungal Properties for Pita Bread Shelf Life Improvement

Ochratoxin A (OTA) is a mycotoxin produced in the secondary metabolism of fungus belonging to the genus Aspergillus and Penicillium. In this study, the employment of oriental mustard flour (OMF) as an ingredient in a packaged sauce was evaluated for the generation in situ of the antimicrobial compound allyl isothiocyanate (AITC) in order to preserve pita bread contaminated with Penicillium verrucosum VTT D-01847, an OTA producer, in an active packaging system. Four different concentrations (8, 16, 33 and 50 mg/g) were tested. Mycelium formation, mycotoxin production, AITC absorbed by the food matrix, and volatilization kinetics were studied for each concentration. The results obtained were compared with bread treated with the commercial additive calcium propionate (E-282). The results showed a shelf life increase of two and three days with the employment of 33 and 50 mg/g of OMF, with a significant reduction of the fungal population (3.1 and 5.7 logs, respectively) in comparison with the control experiment. The use of 16 and 33 mg/g of OMF in the sauce formulation decreased the concentration of OTA in the bread samples while no OTA production was detected employing 50 mg/g of OMF.

Optimizing the Addition of Functional Plant Extracts and Baking Conditions To Develop Acrylamide-Free Pita Bread

ABSTRACTThe effects of using freeze-dried extracts (FDEs) of spearmint (Mentha spicata), fennel (Foeniculum vulgare), and turmeric (Curcuma longa) as well as adjusting the baking temperature and time on acrylamide formation in pita bread were investigated to obtain the most acceptable conditions that produced the lowest acrylamide concentrations. A Box-Behnken design was adopted for optimization of the pita bread formulations by adding FDEs (3 to 25 g/100 g of wheat flour) and adjusting the baking temperature (200 to 300°C) and baking time (3 to 11 min), and the effects of these changes on color parameters, phytochemical attributes, and acrylamide concentrations were evaluated. Increasing the concentration of FDE and decreasing the baking temperature and time considerably decreased the acrylamide concentration in bread for all experimental trials. No acrylamide was detected in pita bread formulated with 25 g of mint FDE/100 g of wheat flour and baked at 250°C for 3 min, formulated with 25 g of mint or fennel FDE/100 g and baked at 300°C for 7 min, formulated with 3 g of mint, fennel, or turmeric FDE/100 g and baked at 200°C for 7 min, formulated with 14 g of mint FDE/100 g and baked at 300°C for 3 min, and formulated with 25 g of mint or fennel FDE/100 g and baked at 200°C for 7 min. Pita breads formulated with fennel and turmeric FDE were given high sensory scores.

Using MR-FTIR and Texture Profile to Track the Effect of Storage Time and Temperature on Pita Bread Staling

Textural deterioration of pita bread, PB, due to staling is an important quality parameter during storage. Loss of freshness due to PB staling results in significant quality and economic loss. PB staling was studied using both MR-FTIR spectroscopy and textural profile including time to rupture and tensile and compressive forces. The study was conducted at room temperature (23°C) and freezing temperature (−18°C) over 96 h of storage time after baking. Some physical properties of PB such as loaf weight, dimensions, water activity, and density were measured. MR-FTIR measurement spectra in the wavelength 900–1150 cm−1 corresponding to the “saccharides” regions and the range 3000–3600 cm−1 corresponding to O-H bond stretching vibration were able to clearly detect the PB deterioration at different storage times as shown by statistical significance test. Mechanical measurements of tearing force, time to rupture, and 25% compression force were also found to be good indicators of PB quality deterioration. Time to rupture, however, was found to be the best PB deterioration indicator. In addition, PB stored at room temperature showed a significant deterioration (toughening) compared to that stored at freezing temperature which showed little or nonsignificant deterioration during storage. High negative correlation, r = -0.97, was observed between the 25% compression force and the wavenumber 960 cm−1 at room temperature.