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Applied Biochemistry and Biotechnology: Part A: Enzyme Engineering and Biotechnology (v.126, #3)
Organic and inorganic fouling at quartz-liquid interface in ultraviolet photoreactors during on-line sterilization of cheese whey by N. S. Mahmoud; A. E. Ghaly (pp. 157-175).
This article reports on lamp fouling during on-line ultraviolet (UV) sterilization of cheese whey. The extent of fouling as well as the composition of fouling materials was studied after the operation of three tubular UV reactors of different flow thicknesses (18, 13, and 6 mm) for 48 h at a 2-h residence time. Lamp fouling, which significantly affected the sterilization efficiency, was realized after an extended period of operation. The extent of lamp fouling increased with a decrease in the thickness of the flowing cheese whey (14.42, 15.31, and 25.25 g for 18-, 13-, and 6-mm thickness, respectively). A strong relationship between the extent of fouling and the steady-state outlet temperature was observed. The rouling material contained 63.51 to 77.19% protein, 12.57 to 16.49% fat and 6.51 to 9.47% minerals on dry weight bases compared with 1% protein, 0.5% fat, and 0.4% minerals in raw cheese whey. The organic and inorganic material concentrations in the fouling material increased with a decrease in the flow thickness. The fouling mechanism was owing to adsorption and direction exchange, which were enhanced by the high temperature and low pH attained in the study. Improved designs of UV reactors in which the contact between the flowing material and the quartz surface should be developed.
Keywords: Ultraviolet radiation; sterilization; cheese whey; lamp fouling; protein; fat; minerals; temperature
Microencapsulated mycelium-bound tannase from Aspergillus niger by Xiao-Wei Yu; Yong-Quan Li (pp. 177-187).
Microencapsulated Aspergillus niger with mycelium-bound tannase activity was employed to investigate the esterification of propyl gallate from gallic acid and propanol in organic solvents. The effects of various organic solvents (log P:−1.0 to 6.6) on the enzymatic reactions showed that benzene (log P:2.0) was the suitable solvent, for which the conversion reached 26.8%. The optimum catalyst concentration and water concentration was found at 25 capsules in 10 mL of benzene and 0.04 g of water/capsule. The external mass transfer effect could be eliminated at stirring speeds of 180 rpm or higher. Both substrates 1-propanol and gallic acid had significant inhibition effects on the tannase activity. Maximum molar conversion (36.2%) was achieved with 9.1% (v/v) 1-propanol and 8 mM gallic acid and decreased with increasing amounts of substrates.
Keywords: Biosynthesis; immobilized cells; Aspergillus niger ; tannase; organic solvents; optimization; propyl gallate; production kinetics
Performance of anaerobic sequencing batch biofilm reactor submitted to different influent volume feeds and cycle time periods maintaining organic loading by Roberto A. Bezerra Jr.; José A. D. Rodrigues; Suzana M. Ratusznei; Marcelo Zaiat; Eugenio Foresti; Walter Borzani (pp. 189-203).
The stability and efficiency of an anaerobic reactor containing biomass immobilized on polyurethane foam were assessed. The reactor with mechanical stirring of 500 rpm and maintained at 30±1°C treated synthetic wastewater with a concentration of approx 500 mg of chemical oxygen demand/L and was fed with different influent volumes and cycle times maintaining organic load. Operation was in batch mode with renewal of only part of the volume of wastewater to be treated; that is reactor discharge was not complete, but partial. The main operational characteristic investigated was the ratio of the volume of wastewater fed per cycle (V A ) to the volume of wastewater in the reactor (V u ) maintaining the same volumetric organic load. This way, operating flexibility could be verified in relation to the volume of treated wastewater at each cycle and the cycle time for the same organic load. The results indicated that the reactor was able to operate with different V A /V u ratios with no significant loss in performance, thus allowing increased operational flexibility. For conditions in which V A was ≥50% of V u , removal efficiencies of filtered and nonfiltered organic matter were about 84 and 79%, respectively, whereas at conditions of higher initial influent dilution, these efficiencies were slightly lower, about 80 and 74%, respectively. At higher initial influent dilutions, it became difficult to maintain a constant reactor medium volume, owing to a high formation rate of viscous polymer-like material, likely of microbiologic origin.
Keywords: Anaerobic sequencing batch reactor; anaerobic treatment; immobilized biomass; feed volume; cycle time; organic load
Effect of hydrocarbons and other parameters on hydrocarbon-utilizing Pichia angusta MTCC-225 by R. Sreenivas Rao; M. A. Rasheed; G. Kalpana; D. J. Patil; B. Kumar (pp. 205-214).
Pichia angusta MTCC-225, a catalase-positive yeast that utilizes methanol and lighter hydrocarbons, is the subject of this investigation. An orthogonal experimental design L16 was used to investigate the effects of methanol, a gas mixture, zero air, temperature, agitation, and salts solution on hydrocarbon utilizing P. angusta. QUALITEK-4 Software was used for automatic design and analysis of the experimental results. Among the various parameters tested, agitation contributed the highest influence (56.5%). Zero air, methanol concentration, and gas mixture showed a moderate influence on the growth of P. angusta. Methanol concentration and gas mixture showed a 10.91 and 10.12% influence, respectively, on yeast growth. Zero air played an important role, with a 15.19% influence on the utilization of hydrocarbon.
Keywords: Hydrocarbons; methanol; orthogonal array; Pichia angusta