The use of an economical medium for the production of alkaline serine proteases by Bacillus licheniformis NH1

The present study is concerned with the selection of new economical media based on agricultural and marine-processing by-products for the production of alkaline proteases by Bacillus licheniformis NH1. Powders from different fish species were prepared and then tested as growth media at a concentration of 10 g/l for proteases production by NH1 strain. Powder prepared from whole Sardinelle was found to be the best substrate for the production of the alkaline protease. The NH1 strain exhibited a slightlygreater protease production (2927 U/ml) in medium containing only whole Sardinelle powder than that obtained in control medium (2800 U/ml). Proteases were produced even when strain NH1 was cultivated in medium containing only powder prepared from combined heads and viscera Sardinelle (CHVSP), about 2117 U/ml. Protease production was also carried out in media containing hulled grain of wheat, a by-product of semolina factories, as carbon source. Maximum activity (2517 U/ml) was achieved when the strain was grown in medium containing hulled grain of wheat (10 g/l), casein peptone (2 g/l), K2HPO4 (0.5 g/l) and KH2PO4 (0.5 g/l). Moreover, protease production was considerably enhanced when thestrain was grown in medium containing both hulled grain of wheat and CHVSP as carbon and nitrogen sources, respectively, (4771 U/ml). The study shows that hulled grain of wheat and powders from fishery by-products could be utilized as bacterial substrates for the production of alkaline proteases by B. licheniformis NH1

Antioxidant properties of Enterobacter cloacae C3 lipopeptides in vitro and in model food emulsion

The present work aims to investigate the in vitro antioxidant activities of Enterobacter cloacae C3 lipopeptides, as well as the stability of sunflower oil in water (o/w) emulsion and the conservation of raw beef patties. The C3 lipopeptides were assayed for their antioxidant activity through five different tests. The C3 lipopeptides showed good in vitro antioxidant activities. Lipopeptides C3 exhibited important antioxidant properties in 10% sunflower o/w emulsions during prolonged storage (28 days) at 30°C. The effect of C3 lipopeptides on the oxidative stability of raw beef patties showed effectiveness effect in preventing oxidative degradation of lipids via thiobarbituric acid reactive substance and peroxide methods. Cytotoxicity test using human kidney HEK293 cells showed that studied lipopeptides was nontoxic substances. The results of this study indicate that lipopeptides C3 could be appropriate antioxidant agent in food models as inhibitors of lipid oxidation.Peer ReviewedPostprint (author's final draft

The conservative effects of lipopeptides from Bacillus methylotrophicus DCS1 on sunflower oil-in-water emulsion and raw beef patties quality

Lipid oxidation was considered as a problem in food conservation. The present study aims to investigate the effect of lipopeptides DCS1 on the conservation of food models against lipid oxidation by determining the primary and the secondary oxidation products. Lipopeptides DCS1 are able to preserve the nutritional properties of the emulsion during 23¿days of storage, at a concentration of 0.0125% (w/w of emulsion), by slowing down the formation of hydroperoxides and malondialdehyde (MDA) compounds. The direct incorporation of lipopeptides in ground beef patties at a concentration of 0.5% (w/w of meat) was found to be more effective than gelatin film enriched with lipopeptides (2.5%, w/w of gelatin) as a coating, in inhibiting lipid oxidation. Furthermore, lipopeptides DCS1 are not toxic to human kidney cells HEK293 up to a concentration of 250¿µg/ml. The results indicate that lipopeptides DCS1 are effective for the preservation of fatty foods against lipid oxidation.Peer ReviewedPostprint (author's final draft

Structural characterization and identification of cyclic lipopeptides produced by Bacillus methylotrophicus DCS1 strain

Bacillus methylotrophicus DCS1 strain was isolated from diesel contaminated soil and screened for its ability to produce biosurfactants; it was found effective for the production of surface active molecules. The structural characterization of the isolated lipopeptides was studied by a variety of analytical techniques. The organic extract of DCS1 'lipopeptides was fractionated by silica gel column chromatography (60 Mesh). Fractions containing lipopeptides were collected and identified by tandem mass spectrometry MALDI-TOF-MS and MALDI-TOF MS2. The crude biosurfactants contains a mixture of homologous lipopeptides with molecular weights between 1016 and 1556 Da. Mass spectrometry analysis of partially purified lipopeptides revealed that it contains different isoforms belonging to three families: surfactin, iturin and fengycin. To identify lipopeptides isoforms, MALDI-TOF MS2 was used and ions representing characteristic fragmentations were detected. The mass spectrometry characterization revealed the presence of four variants of surfactin lipopeptides, four variants of pumilacidin that differ according to the-beta-hydroxy fatty acid chain length as well as the type of amino acid at position 7, five variants of iturin A/mycosubtilin varying in the beta-amino fatty acid chain length from C12 to C16, C16 iturin Cl, five isoforms of bacillomycin D varying in the beta-amino fatty acid chain length from C14 to C18, and six fengycin isoforms that differ according to the length of the beta-hydroxy fatty acid side chain as well as the amino acid at position 6. The capacity of B. methylotrohicus DCS1 strain to produce many lipopeptides isoforms belonging to different families and having a structural diversity is a very interesting characteristic that allows them to be used in various fields of biotechnological applications

Enhancement of Surfactin and Fengycin Production by Bacillus mojavensis A21: Application for Diesel Biodegradation

This work concerns the study of the enhancement of surfactin and fengycin production by B. mojavensis A21 and application of the produced product in diesel biodegradation. The influences of the culture medium and cells immobilization were studied. The highest lipopeptides production was achieved after 72 hours of incubation in a culture medium containing 30 g/L glucose as carbon source and a combination of yeast extract (1 g/L) and glutamic acid (5 g/L) as nitrogen sources with initial pH 7.0 at 30°C and 90% volumetric aeration. The study of primary metabolites production showed mainly the production of acetoin, with a maximum production after 24 h of strain growth. The use of immobilized cells seemed to be a promising method for improving lipopeptides productivity. In fact, the synthesis of both lipopeptides, mainly fengycin, was greatly enhanced by the immobilization of A21 cells. An increase of diesel degradation capacity of approximately 20, 27, and 40% in the presence of 0.5, 1, and 2 g/L of produced lipopeptides, respectively, was observed. Considering these properties, B. mojavensis A21 strain producing a lipopeptide mixture, containing both surfactin and fengycin, may be considered as a potential candidate for future use in bioremediation and crop protection

Real-Time Low-Cost Speed Monitoring and Control of Three-Phase Induction Motor via a Voltage/Frequency Control Approach

In this paper, a new design of a real-time low-cost speed monitoring and closed-loop control of the three-phase induction motor (IM) is proposed. The proposed solution is based on a voltage/frequency (V/F) control approach and a PI antiwindup regulator. It uses the Waijung Blockset which considerably alleviates the heaviness and the difficulty of the microcontroller’s programming task incessantly crucial for the implementation and the management of such complex applications. Indeed, it automatically generates C codes for many types of microcontrollers like the STM32F4 family, also used in this application. Furthermore, it offers a cost-effective design reducing the system components and increasing its efficiency. To prove the efficiency of the suggested design, not only simulation results are carried out for a wide range of variations in load and reference speed but also experimental assessment. The real-time closed-loop control performances are proved using the aMG SQLite Data Server via the UART port board, whereas Waijung WebPage Designer (W2D) is used for the web monitoring task. Experimental results prove the accuracy and robustness of the proposed solution

A New Direct Speed Estimation and Control of the Induction Machine Benchmark: Design and Experimental Validation

Speed sensorless control schemes have potential benefits for industrial applications because they contribute to reducing process cost and they avoid using fragile sensors as encoders or resolvers in hostile environment. In addition, simplicity, reliability, and fast response of control structures to signal commands are much-needed features. In this paper, a new Speed Sensorless Direct Control (SSDC) technique allowing the achievement of these objectives is proposed. This technique combines Field Oriented Control (FOC) and Direct Torque Control (DTC) properties in the same approach. The estimated speed is reached only according to the measured current and voltage of the stator. DTC is extended to speed sensorless direct control with any notable modification. The proposed scheme is implemented to the induction machine benchmark and evaluated in real time under various possible scenarios of use. Experimental results show that the proposed SSDC has interesting capabilities to conduct induction motor in real time operation with good accuracy