Study of the production of fructose and ethanol from sucrose media by Saccharomyces cerevisiae.

The production of ethanol and enriched fructose syrups from a synthetic medium with various sucrose concentrations using the mutant Saccharomyces cerevisiae ATCC 36858 was investigated. In batch tests, fructose yields were above 90% of theoretical values for the sucrose concentrations between 35 g/l and 257 g/l. The specific growth rates and biomass yields were from 0.218 to 0.128 h(-1) and from 0.160 to 0.075 g biomass/g of glucose and fructose consumed, respectively. Ethanol yields were in the range of 72 to 85% of theoretical value when sucrose concentrations were above 81 g/l. The volumetric ethanol productivity was 2.23 g ethanol/(l h) in a medium containing 216 g/l sucrose. Fructo-oligosaccharides and glycerol were also produced in the process. A maximum fructo-oligosaccharides concentration (up to 9 g/l) was attained in the 257 g/l sucrose medium in the first 7 h of the fermentation. These sugars started to be consumed when the concentrations of sucrose in the media were less than 30% of its initial values. The fructo-oligosaccharides mixture was composed of 6-kestose (61.5%), neokestose (29.7%) and 1-kestose (8.8%). The concentration of glycerol produced in the process was less than 9 g/l. These results will be useful in the production of enriched fructose syrups and ethanol using sucrose-based raw materials.

Predictions of binary sorption isotherms for the sorption of heavy metals by pine bark using single isotherm data.

The adsorption of three heavy metal ions by pine bark was studied. The study was divided into two parts; single component adsorption of the metals Cu2+, Cd2+ and Ni2+ and bisolute adsorption of the three binary systems Cu2+-Cd2+, Cu2+-Ni2+ and Cd2+-Ni2+. Extended Langmuir model, extended Freundlich model. Sips model and ideal adsorption solution theory (IAST) models were used to predict the equilibrium uptake for Cu2+, Cd2+ and Ni2+ in the binary diluted solutions using the single adsorption constants. The experimental data of single isotherm adsorption process were found to follow Langmuir isotherm model with less accuracy than Freundlich and Sips models. Whereas, the predictions of bisolute adsorption isotherms of the mentioned three systems, Cu2+-Cd2+, Cu2+-Ni2+ and Cd2+-Ni2+, showed good agreement with experimental data when using Extended-Langmuir, Extended-Freundlich and IAST. However, the only good fit of the Sips model was with the Cu2+-Cd2+ system.

A method for the decrease of phenolic content in commercial canola meal using an enzyme preparation secreted by the white-rot fungus Trametes versicolor.

An enzymatic process for upgrading the quality of canola meal (CM) by decreasing its phenolic content was investigated. The new method was based on the addition of the enzyme preparation from white-rot fungus Trametes versicolor to the meal-buffer slurry. A 98% decrease in the concentration of SAE was observed after 1 h of the treatment. The following process variables were considered for optimizing the process: pH, temperature, enzyme, meal, and oxygen concentrations. It was found that: (1) the natural buffering capacity of CM resulted in a negligible effect of the pH of the buffer, which was used as the continuous phase in the process, on the extent of decrease in sinapic acid esters (SAE); (2) the system was saturated with the enzyme when its concentration was 4 nkat/mL of the continuous phase; and (3) the optimum temperature was 50 degrees C. The process could be carried out even at higher temperatures due to the protective action of CM, which resulted in an increase in the thermal stability of the enzyme. The particle size influenced the extraction of the SAE from the meal, indicating that, at lower SAE concentrations, the process became diffusion limited. This result, together with those showing no effect of the intensity of agitation, indicated that the enzymatic process can be characterized by high Biot numbers. During the enzymatic process, the molar concentration of available oxygen can become a limiting factor when it is more than four times lower than the molar concentration of phenolics in the treated meal. The new enzymatic method was compared with other methods reported in the literature for the decrease in the phenolic content of rapeseed meals. It was found that, among the methods tested, the enzymatic treatment was the most effective, followed by the lime treatment. The enzymatic process did not reduce the quality of the protein isolates prepared from the CM. After the addition of a simple acetone-washing step, the isolate from the enzymatically treated meal had even better properties. Copyright 1999 John Wiley & Sons, Inc.

Transformation of 3,5-dimethoxy,4-hydroxy cinnamic acid by polyphenol oxidase from the fungus Trametes versicolor: product elucidation studies.

Sinapic acid (SA), 3,5-dimethoxy,4-hydroxy cinnamic acid, was incubated with a crude polyphenol oxidase from the fungus Trametes versicolor. Some products of this transformation were isolated and their structures identified using mass spectrometry, nuclear magnetic resonance and Fourier transform infrared spectroscopy, and X-ray crystallography. It was found that the enzymatic oxidation of SA includes two distinct phases. In the initial phase SA is enzymatically transformed to r-1H-2c,6c-bis-(4'-hydroxy-3', 5'-dimethoxyphenyl)-3,7-dioxabicyclo-[3,3,0]-octane-4,8-dione, dehydrodisinapic acid dilactone. The mechanism of this reaction may involve coupling of two phenoxy radicals by the beta-beta mode and subsequent intramolecular nucleophilic attack. In the second phase dehydrodisinapic acid dilactone is transformed by polyphenol oxidase into several intermediate products, including 4-(4-(3, 5-dimethoxy-4-oxo-2,5-cyclohexadienyliden)-1, 4-dihydroxy-(E)-2-butenylidene)-2,6-dimethoxy-2, 5-cyclohexadien-1-one. The final product of the overall transformation of SA is 2,6-dimethoxy-p-benzoquinone. The obtained results were used to propose a part of the transformation pathway for the enzymatic oxidation of SA by polyphenol oxidase.

Modeling the enzymatic transformation of 3,5-dimethoxy,4-hydroxy cinnamic acid by polyphenoloxidase from the white-rot fungus Trametes versicolor.

A mechanism for transforming sinapic acid by a polyphenoloxidase from Trametes versicolor was investigated using changes in sinapic acid and oxygen concentrations during the reaction. The experiments were performed in a closed system without supplemental oxygen. The effects of temperature and initial oxygen concentration on the reaction rates were examined. To compare the obtained results with those from spectrophotometric studies, some runs were performed using an open system with supplemental oxygen. Sinapic acid transformation can be described by the Theorell-Chance Bi-Bi or Ordered Bi-Bi mechanisms. This reacting system consisted also of additional enzymatic reactions between the products of sinapic acid transformation and oxygen. A mathematical model was developed using four ordinary differential equations that represent the Theorell-Chance Bi-Bi mechanism with three alternate substrates. Model parameters (i.e., rate constants) were determined using the data collected at three different temperatures. On the basis of the transition state theory, relationships between these constants and temperature were established. It is shown that, in the open system, the observed change in the enzyme activity at higher temperatures was caused by two opposing phenomena: an Arrhenius effect which increased the rate, and a solubility effect which reduced the rate due to a lower oxygen concentration. This finding allows us to recommend better conditions for spectrophotometric methods, the assay most commonly used to evaluate this and similar enzymes.

Comparison of 3 methods for the determination of sinapic acid ester content in enzymatically treated canola meals.

The enzymatic reduction of sinapic acid ester content in canola meal using polyphenol oxidase from the fungus T. versicolor was investigated. To determine the effectiveness of this new process, the results obtained using two spectrophotometric methods and an HPLC analytical method for assaying sinapic acid ester content in the treated and untreated meals were compared. It was found that all the methods gave practically the same results when the samples from untreated canola meals were analysed. However, both of the spectrophotometric methods overestimated the sinapic acid ester content in the enzymatically treated meal by 7%-20%, as compared to the results obtained using HPLC. It was found that the sensitivity limits for the spectrophotometric methods used for the determination of sinapic acid ester content in enzymatically treated canola meals were 2.67 g and 1.47 g phenolics/kg meal for the direct and chemical spectrophotometric methods respectively. A correlation between the results obtained using the spectrophotometric and HPLC methods is given. The enzymatic treatment resulted in a negligible amount of phenolics in the treated meal.

Adsorption of copper and chromium by Aspergillus carbonarius.

Aspergillus carbonarius NRC 401121 adsorbs some copper and chromium from their solutions. The amount of the adsorbed metal per unit of biomass increased with a decrease in the biomass concentration. The increases in the initial concentrations of metals and pH of the solutions resulted in an increase in copper and chromium uptake. The optimum temperature for copper uptake was 25 degrees C. Heating of the biomass prior to utilizing it in the adsorption tests decreased its metal adsorption capacity. Preincubation of the biomass with glucose enhanced the metal adsorption. The optimum glucose concentration in this process was 0.1%.

The effect of phosphate concentration on phytase production and the reduction of phytic acid content in canola meal by Aspergillus carbonarius during a solid-state fermentation process.

The use of canola meal, an abundant side-product of canola oil processing in Canada, as animal feed is hampered by high phytic acid levels that reduce metal cation availability. Aspergillus carbonarius grows well in a solid canola meal medium, produces phytase and reduces the phytic acid content to zero. Inorganic phosphate addition at a concentration of 1 mg and 5 mg/110 g solid-state culture system results in better growth of the microorganism, higher rates and levels of phytase production, and faster reduction of phytic acid content. Phosphate concentrations of 50 mg and 100 mg/110 g inoculated system had a negative effect affecting primarily the initial rates of biomass and phytase production and phytic acid content reduction. Models that predict biomass production (expressed as glucosamine content) and phytase, as well as the reduction of phytic acid content in the solid-state cultures supplemented with phosphate are reported. They fit the experimental results reasonably well (with a maximum deviation of 7%).

Phytase production and decrease of phytic acid content in canola meal byAspergillus carbonarius in solid-state fermentation.

Solid-state fermentation (SSF) usingAspergillus carbonarius with canola meal as a substrate showed that production of phytase was associated with growth; maximum activity was achieved after 72 h. Apparent 25% and 10% increases in the protein content of the canola meal were noticed after 48 h and 72 h, respectively but total carbohydrate concentration had fallen by 25% by the end of fermentation. The rate of decrease of phytic acid content was optimum with a moisture content between 53% and 60%; homogenization of the inoculum for 120 s led to the greatest biomass and lowest phytic acid content. Inoculation of sterile meal led to lower phytic acid contents than inoculation of non-sterile meal.

Production of alcohol from Jerusalem artichokes by yeasts.

Various yeasts such as several strains of Saccharomyces diastaticus, S. cerevisiae, and Kluyveromyces fregilis were investigated for their ability to ferment the carbohydrates from Jerusalem artichokes to alcohol. Juice extracted of the carbohydrates. Fermentation was also carried out with raw artichokes without prior juice extraction. Result indicate that this row material has good potential for fuel alcohol production by fermentation.

Fuel alcohol biosynthesis by Zymomonas anaerobia: Optimization studies.

The optimum operating conditions for growth and ethanol production of Zymomonas anaerobia ATCC 29501 were established. The optimum pH range and temperature were found to be 5.0-6.0 and 35 degrees C, respectively. Based on the results obtained from the temperature optimization study, an Arrhenius-type temperature relationship for the specific growth rate was developed. The growth and ethanol production of this microbe also have been optimized in terms of concentrations of glucose, essential nutrients, and minerals. With optimum medium and operating conditions, an ethanol concentration of 96 g/L was obtained in 23 h. Both growth and ethanol yield coefficients in dependence on initial glucose concentrations were determined.

Production of surfactant by Arthrobacter paraffineus ATCC 19558.

A. paraffineus ATCC 19558 grown in MMSM (modified mineral salts medium) containing hydrocarbon produced surfactant, with a maximum CMC(-1) value obtained by using hexadecane as the carbon source. No activity of surface active agent in whole broth was observed when glucose was used in the MMSM instead of hexadecane. The biomass concentration obtained with glucose was about 40% of that obtained with hexadecane. Glucose (4%) in the medium containing hexadecane caused a 27 and 21% decrease of biomass and surfactant concentrations, respectively. In the process of surfactant production, glucose can be used as a carbon source for growth, and hexadecane added later can serve for production of the surface active agent. The optimum temperature for production of surfactant is 27 degrees C.

Protoplasts obtained from Candida tropicalis grown on alkanes.

A method for the preparation of protoplasts from Candida tropicalis cultivated on n-tetradecane is described. This essentially consists of replacing the mannitol-sorbitol solution of the classical helicase technique by 1 m magnesium sulfate and lowering the pH to 4.1 during incubation in the presence of helicase. The protoplasts thus prepared behave like intact cells and are capable of consuming oxygen in the presence of n-tetradecane, n-decane, 1-decanol, and glucose.