A broth of yeast cells cultivated in molasses was crossfiltered with a thin-channel module. The permeation flux gradually decreased at a constant cell concentration. The flux was much lower than that obtained for yeast broth cultivated in yeast extract, polypeptone, and dextrose (YPD) medium during the filtration. The flux did not depend on the membrane pore size (0.45 to 5 mum). The steady-state flux was one-twentieth that calculated for a cake filtration mode from the amount of cake per unit filtration area and the specific resistance of the cake measured in a dead-end filtration apparatus. The lower flux was due to small particles (most of which were less than 1 mum in diameter) in the molasses. The mehanism of crossflow filtration of broths of yeast cells cultivated in molasses was clarified by analysis of the change in flux with time and observations with scanning electron microscopy. At the initial stage of crossflow filtration the yeast cells and particles from the molasses were deposited on the membrane to form the molasses were deposited on the membrane to form a cake in a similar way to dead-end filtration. After the deposition of cells onto the membrane ceased, the fine particles from molasses formed a thin layer, which had higher resistance than the cake formed next to the membrane. The backwashing method was effective to increase the flux. The flux increased low when the pore size was 0.45 to 0.08 mum, but using larger pores of 3 to 5 mum it returned almost to the bases line. (c) 1994 John Wiley & Sons, Inc.

Factors affecting the performance of crossflow filtration were investigated with a thin-channel module and yeast cells. In crossflow filtration of Saccharomyces cerevisiae cells cultivated with YPD medium (Yeast extract, polypeptone, and dextrose) and suspended in saline, a steady state was attained within several minutes when the cell concentration was low and the circulation flow rate was high. The steady-state flux and the change in flux during the initial unsteady state were explained well by conventional filtration theory, with the amount of cake deposited and the mean specific resistance to the cake measured in a dead-end filtration apparatus used in calculation. When the circulation flow rate was lower than a critical value, a part of the channel of the crossflow filtration module was plugged with cell cake, and thus the steady-state flux was low. In crossflow filtration of suspensions of commercially available baker's yeast, the flux gradually decreased, and the flux after 8 h of filtration was lower than the value calculated by filtration theory. Fine particles contaminating the baker's yeast was responsible for the decrease. A similar phenomenon was responsible for the decrease. A similar phenomenon was observed in crossflow filtration of a broth of S. cerevisiae cells cultivated in molasses medium, which also contains such particles, had no effect of the permeation flux during crossflow filtration.

The effects of invert soaps with sodium hydroxide on infectious bursal disease virus (IBDV) were studied. Didecyldimethylammonium chloride was most effective, followed by alkylbenzyldimethylammonium chloride and [mono-bis(tri-methylammonium-methylene chloride)]-alkyl (C9-15) toluene. Dilutions without NaOH had little effect on virus titer. Didecyldimethylammonium chloride was further tested for its effects on IBDV by varying temperature, concentration of invert soap, and pH of the dilution. The effect of the invert soap was strong at 40 C, moderate at room temperature, and weak at 4 C. The concentration of invert soap influenced its efficacy at room temperature but not at 4 C. At pH values below 12.9, the invert soap showed decreased efficacy.

The azo-hydrazone tautomerism of 4-phenylazo-l-naphthol (PAN) in the mixtures of water and organic solvents (alcohols such as methanol, ethanol, n-propanol and t-butanol, ethylene glycol and glycerine, and nonhydroxylic solvents such as dioxane and acetone) was studied spectrophotometrically.The equilibrium constants (Kr) of the tautomerism were obtained. The effects of the composition of the mixture solvent on the KT value were examined. The Kr values were found to increase with an increase in water contents in the mixtures. In monohydric primary alcohol-water mixtures, the KT values were smaller in the mixtures of less polar alcohols. In ethylene glycol-and glycerine-water mixtures, the Kr values were supposed to be dependent upon the sum of water and OH concentrations. In nonhydroxylic solvent-water mixtures log Kr was propor tional to the water concentration in the mixtures. In the mixtures of predominantly aqueous compositions the Kr values sharply increase with an increase of aqueous compositions. These results can be explained by assuming that the Kr values are not dependent upon the bulk solvent properties but dependent upon the microenviron mental properties of PAN molecules. The tautomerism of PAN in the mixtures is almost athermic. The results suggest that the disperse dye in organic solvent-water mixtures is supposed to be in the more hydrophobic environment than the bulk.

A compound disinfectant, which consisted of didecyldimethylammonium chloride (DDAC), ortho-dichlorobenzene (1,2-dichlorobenzene, ODB), and chlorocresol (4-chloro-3-methylphenol, CC), and its component chemicals were individually tested for effectiveness against bovine herpes virus type 1 (BHV-1). DDAC, DDAC+ODB, DDAC+CC, and DDAC+ODB+CC showed effectiveness against BHV-1 at room temperature. However, ODB, CC, and ODB+CC showed no virucidal effects. The effects of all disinfectants tested were decreased at low temperature. DDAC showed disinfectant effects at a dilution of 1/800 and DDAC+ODB, DDAC+CC, and DDAC+ODB+CC at dilutions of 1/800 and 1/1600 at low temperature in the presence of 2% fetal bovine serum (FBS) but ODB, CC, and ODB+CC showed no virucidal effects. At low temperature and in the presence of 10% FBS, DDAC, DDAC+ODB, and DDAC+CC showed disinfectant effects at dilutions of 1/800, whereas ODB, CC, and ODB+CC showed no virucidal effects. DDAC+ ODB+CC was more effective (at 1/800 and 1/1600) than the other disinfectants under these conditions. In conclusion, a combination of three disinfectant components (DDAC+ODB+CC), enhanced the disinfectant effects at low temperature and in organic matter contamination.