Raoudha Ellouz Ghorbel

New Thermostable Amylase from Bacillus cohnii US147 with a Broad pH Applicability

A new thermophilic bacterial strain identified as Bacillus cohnii US147 was isolated from the southern Tunisian soil. The identification was based on physiological tests and molecular techniques related to the 16S ribosomal ribonucleic acid. The isolated strain produced amylase, which was purified. This amylase had an apparent molecular mass of 30xa0kDa as estimated by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis. Amylase US147 showed Km and Vmax values of 0.7xa0mg/ml and 2.2xa0U/ml, respectively, with starch as the substrate. The enzyme was active in acid and basic pH and had a maximal activity on starch at pHxa09 and 70 °C. The enzyme was stable at pHxa09 for 72xa0h and retained half of its activity after incubation at 70 °C for 150xa0min. A partially inhibition (15%, 25%, 23%, 20%, and 22%) was obtained with 1xa0mM SDS, 1xa0mM NaBO3, 1xa0mM H2O2, 1xa0mM Zn+2, and 5xa0mM ethylenediamine tetraacetic acid (EDTA), respectively. The amylase recovered its original activity by the addition of 10xa0mM Ca 2+ to the 5xa0mM EDTA. These properties indicated a possible use of this amylase in starch saccharification, in detergent, and in other industrial applications.

Purification and Characterization of a Low Molecular Weight of β-Mannanase from Penicillium occitanis Pol6

The highest β-mannanase activity was produced by Penicillium occitanis Pol6 on flour of carob seed, whereas starch-containing medium gave lower enzymes titles. The low molecular weight enzyme was purified to homogeneity by ammonium sulfate precipitation, gel filtration, and ion-exchange chromatography procedures. The purified β-mannanase (ManIII) has been identified as a glycoprotein (carbohydrate content 5%) with an apparent molecular mass of 18xa0kDa. It was active at 40xa0°C and pH 4.0. It was stable for 30xa0min at 70xa0°C and has a broad pH stability (2.0–12.0). ManIII showed Km, Vmax, and Kcat values of 17.94xa0mg/ml, 93.52xa0U/mg, and 28.13xa0s−1 with locust bean gum as substrate, respectively. It was inhibited by mannose with a KI of 0.610−3xa0mg/ml. ManIII was activated by CuSO4 and CaCl2 (2.5xa0mM). However, in presence of 2.5xa0mM Co2+, its activity dropped to 60% of the initial activity. Both N-terminal and internal amino acid sequences of ManIII presented no homology with mannanases of glycosides hydrolases. During incubation with locust bean gum and Ivory nut mannan, the enzyme released mainly mannotetraose, mannotriose, and mannobiose.

Recent advances in Rosaceae gum exudates: From synthesis to food and non-food applications

In recent years, great interest has been devoted to the development of new applications for natural gums. These molecules were used for a variety of purposes since they are chemically inert, non-toxic, less expensive, biodegradable and widely available. They represent one of the most abundant raw materials used not only in commercial food products, but also in cosmetic and pharmaceutical products. Plant gums take their advantages compared to other gums (e.g., from animal and microbial sources) mainly because of their acceptance by consumers. Despite of the well description given in literature for the features of plant gum exudates, there is a lack distinguishing the different families that are producing gums, and their potential applications. Among these gums, the ones produced by Rosaceae family (e.g., almond, apricot, cherry, peach, and plum plants) have been taking special attention. Thus, the aim of this review is to report the recent advances in Rosaceae gum exudates. An emphasis is given for the formation mechanisms of these gums, their chemical composition, functional properties and structures, beneficial properties, as well as their food/non-food applications.

Improved Mannanase Production from Penicillium occitanis by Fed-Batch Fermentation Using Acacia Seeds

By applying a fed-batch strategy, production of Penicillium occitanis mannanases could be almost doubled as compared to a batch cultivation on acacia seeds (76 versus 41u2009U/mL). Also, a 10-fold increase of enzyme activities was observed from shake flask fermentation to the fed-batch fermentation. These production levels were 3-fold higher than those obtained on coconut meal. The high mannanase production using acacia seeds powder as inducer substrate showed the suitability of this culture process for industrial-scale development.

The effect of sodium lactate and lactic acid combinations on the microbial, sensory, and chemical attributes of marinated chicken thigh

The present study was undertaken to evaluate the chemical, microbiological, and sensory effects of different sodium lactate (SL) and lactic acid (LA) combinations on marinated chicken thigh. The latter were treated with SL and LA combined at various concentrations, namely 0.3 and 0.03; 0.5 and 0.05; 0.6 and 0.06; 0.75 and 0.075; and 0.9 and 0.09%, respectively. The findings indicated that those combinations were efficient (P < 0.05) against the proliferation of various spoilage microorganisms, including aerobic plate count, psychrotrophic populations, Pseudomonas spp., Staphylococcus aureus, Enterobacteriaceae, and Salmonella spp. The results from chemical analyses revealed that the treated thigh underwent significant decreases (P < 0.05) in terms of pH values and total volatile base nitrogen contents. Significant differences (P < 0.05) were, however, detected with regard to their sensory attributes, with SL-LA concentrations of 0.9 and 0.09 yielding the highest scores for the color, texture, and flavor attributes. Overall, the findings demonstrated that the addition of 0.9% SL and 0.09% LA to marinated chicken can help delay the proliferation of spoilage microorganisms, prevent the generation of undesirable chemicals, improve the levels of sensory attributes, and extend the shelf life of products during refrigerated storage.