Maryam Hashemi

Development of a solid-state fermentation process for production of an alpha amylase with potentially interesting properties.

Ca-independency with potential activity and stability at low pH are among the most interesting characteristics of alpha-amylase in starch industry. In this attempt the synergetic effect of low pH on activity of crude Ca-independent alpha-amylase isolated from a native Bacillus sp. KR-8104 in solid-state fermentation (SSF) was studied using wheat bran (WB) as a substrate. The effects of different parameters including moisturizing agents, solid substrate to moisture ratio, particle size, incubation temperature and period, inoculum (v/w) and supplementation with 1% (w/w) different carbon and nitrogen sources on enzyme production were investigated. Maximum enzyme production of 140U/g dry fermented substrate was obtained from wheat bran moistened with tap water at a ratio of 1:1.5 and supplemented with 1% (w/w) NH(4)NO(3) and 1% (w/w) lactose after 48h incubation at 37 degrees C. Even though the production of alpha-amylase was lower at 40 and 45 degrees C, the viable cell count was higher. In addition response surface methodology (RSM) was applied to find optimum conditions of temperature and pH on crude amylase activity. Using central composite design (CCD) a quadratic mathematical model equation was derived for the prediction of enzyme activity. The results showed that the model was in good agreement with experimental results, with R(2)=0.90 (p<0.0001) and the low pH has a synergetic effect on enzyme activity at higher temperature.

Preparation and characterization of a novel bionanocomposite edible film based on pectin and crystalline nanocellulose

In this study, for the first time, the edible pectin film was reinforced by crystalline nanocelullose (CNC). The incorporation of three levels of CNC (2, 5 and 7% w/w) on mechanical, thermal and water vapor barrier properties of pectin-based biodegradable film were investigated using solution casting evaporation method for film preparation. The optimum result was obtained through the nanocomposite film with 5% CNC in terms of mechanical and water vapor properties as the tensile strength increased up to 84% and water vapor permeability decreased by 40%. However, analysis of thermal properties indicated no significant effect of CNC on glass transition temperature. X-ray diffraction (XRD) studies illustrated a positive correlation between the degree of crystallinity and the CNC level. Moreover, AFM images presented good dispersion of CNC in the pectin matrix suggesting appropriate interaction between the filler and matrix, which is in agreement with mechanical consequences. According to the overall results, the reinforcement of pectin film with 5% CNC compared to other strengthening strategies had a higher effect and therefore it could be introduced as a good candidate for the development of strong, completely biodegradable and renewable food packaging material.

The potential of brewer's spent grain to improve the production of α-amylase by Bacillus sp. KR-8104 in submerged fermentation system.

Brewers spent grain (BSG) was used as a solid substrate for the production of α-amylase by Bacillus sp. KR-8104 in a submerged fermentation system. The production of α-amylase was maximized through statistical optimization of the BSG concentration and incubation time using the Doehlert experimental design. The highest tested amount of BSG (5%, w/v) in the optimization process resulted in a 5.1-fold enhancement of the response. Subsequently, we studied the role of the water-soluble and -insoluble fractions of BSG in the production of α-amylase. The results revealed that whole BSG had a greater effect on the production of α-amylase than each fraction had separately. Finally, when we examined the potential of BSG to replace the constituents of a medium formula, we observed that simultaneously adding BSG, omitting dextrin, and reducing the other ingredients concentration in the culture medium improved the production of α-amylase and made the production process more economical.

Ion pair-based dispersive liquid-liquid microextraction followed by high performance liquid chromatography as a new method for determining five folate derivatives in foodstuffs.

A novel technique for simultaneous determination of five folate derivatives in various food matrices was developed by ion pair-based dispersive liquid-liquid microextraction (IP-DLLME) combined with high-performance liquid chromatography (HPLC). In the proposed method, N-methyl-N,N-dioctyloctan-1-ammonium chloride (aliquat-336) was used as an ion-pair reagent. Effective variables of microextraction process were optimized. Under optimum conditions, the method yielded a linear calibration curve ranging from 1-200 ng g(-1) with correlation coefficients (r(2)) higher than 0.98. The relative standard deviation for the seven analyses was 5.2-7.4%. Enrichment factors for the five folates ranged between 108-135. Limits of detection were 2-4.1 ng g(-1). A comparison of this method with other methods described that the new proposed method is rapid and accurate, and gives very good enrichment factors and detection limits for determining five folate derivatives. The newly developed method was successfully applied for the determination of five folate derivatives in wheat flour, egg yolk and orange juice samples.

Furanic compounds and furfural in different coffee products by headspace liquid-phase micro-extraction followed by gas chromatography–mass spectrometry: survey and effect of brewing procedures

In this study, the levels of furan, 2-methylfuran, 2,5-dimethylfuran, vinyl furan, 2-methoxymethyl-furan and furfural in different coffee products were evaluated. Simultaneous determination of these six furanic compounds was performed by a head space liquid-phase micro-extraction (HS-LPME) method. A total of 67 coffee powder samples were analysed. The effects of boiling and espresso-making procedures on the levels of furanic compounds were investigated. The results showed that different types of coffee samples contained different concentrations of furanic compounds, due to the various processing conditions such as temperature, degree of roasting and fineness of grind. Among the different coffee samples, the highest level of furan (6320 µg kg−1) was detected in ground coffee, while coffee-mix samples showed the lowest furan concentration (10 µg kg−1). Levels in brewed coffees indicated that, except for furfural, brewing by an espresso machine caused significant loss of furanic compounds.

PROCESS PARAMETERS STUDY OF α-AMYLASE PRODUCTION IN A PACKED-BED BIOREACTOR UNDER SOLID-STATE FERMENTATION WITH POSSIBILITY OF TEMPERATURE MONITORING

Production of α-amylase in a laboratory-scale packed-bed bioreactor by Bacillus sp. KR-8104 under solid-state fermentation (SSF) with possibility of temperature control and monitoring was studied using wheat bran (WB) as a solid substrate. The simultaneous effects of aeration rate, initial substrate moisture, and incubation temperature on α-amylase production were evaluated using response surface methodology (RSM) based on a Box–Behnken design. The optimum conditions for attaining the maximum production of α-amylase were 37°C, 72% (w/w) initial substrate moisture, and 0.15 L/min aeration. The average enzyme activity obtained under the optimized conditions was 473.8 U/g dry fermented substrate. In addition, it was observed that the production of enzyme decreased from the bottom of the bioreactor to the top.

Comparison of phytochemical constituents and antioxidant activities of aqueous and alcoholic extracts of saffron

In the present work, phytochemical compounds and antioxidant activities of three aqueous, ethanolic (50 and 80%, v/v) and methanolic (50 and 80%, v/v) extracts of saffron during 1 and 24 h of shaking time were compared. Results showed that the ethanolic solution (80%, v/v) extracted for 24 h had the highest amounts of phenolic compounds (29.2 g gallic acid (Gal)/g dry weight (DW)), followed by 1 h aqueous extract (17.53 mg Gal/g DW) and 1 h methanol extract (50%, v/v, 14.5 mg Gal/g DW). The total flavonoid contents for all extracts were varied from 0.20 to 0.56 mg quercetin/g DW. Although all the extracts were capable to scavenge the 2,2′-diphenyl-1-picrylhydrazyl free-radical, ethanolic extract was found to be the best antioxidant activity (84.22%). Solvent type and extraction time had significant effects on the antioxidant capacities and phytochemical contents of the saffron extracts. A significant positive correlation was found between the antioxidant activity, total phenolic (r2=0.991) and flavonoid (...

Biodegradation of heptadecane in hydrocarbon polluted dune sands using a newly-isolated thermophilic bacterium, Brevibacillus borstelensis TMU30: statistical evaluation and process optimization

An enrichment culture was established to isolate a thermophilic hydrocarbon-degrading bacterium from contaminated soil samples from the Tehran Petroleum Refinery. The bacterium was characterized based on 16S rRNA and identified as Brevibacillus borstelensis TMU30. It is registered at NCBI under accession number KF181624.1. The capability of the bacterium for degradation of heptadecane as a representative contaminant in polluted dune sand was evaluated in a slurry bubble column bioreactor. The aeration rate, inoculum content and pulp density were optimized to maximize the degradation of heptadecane using the central composite design of response surface methodology. The results showed that maximum heptadecane reduction reached 48% at an aeration rate of 62 ml min−1, inoculum content of 9.3% (v/v) and pulp density of 63 g l−1 only after 4 days. This study highlights an important potential use of thermophilic degradative bacteria to eliminate contamination in a slurry bioreactor while shortening dramatically the treatment time.

Enhancement of xylanase productivity using industrial by-products under solid suspended fermentation in a stirred tank bioreactor, with a dissolved oxygen constant control strategy

Solid suspended fermentation of Bacillus subtilis D3d using different agro-industrial residues was performed in this work for the co-production of xylanase and lichenase. Based on the results, brewers spent grain (BSG) and corn steep liquor (CSL) combination were selected for further studies. The central composite design with the aim of maximum enzyme production at minimum fermentation time indicated 2.5% BSG and 0.5% CSL at 42 h as the best conditions for highest productivity in the shake flask. The results revealed that CSL at a high level can lead to a reduction in enzyme productivity. In a 2 L stirred tank bioreactor, the productivity of xylanase reached a peak of 10 U mL−1 h−1 using a dissolved oxygen (DO)-constant control strategy at 50% air saturation. Lichenase production increased 1.7 times, but the productivity of this enzyme was not affected by DO levels. The physiological state of solid suspended fermentation was investigated by carbon dioxide evolution rate (CER) and oxygen transfer rate (OTR) through off gas analyzer data.