Continuous propagation ofKluyveromyces fragilis in cheese whey for pollution potential reduction

A 25-L working volume, upright cylindrical fermenter made of stainless steel was used to investigate cheese whey yeast fermentation for pollution potential reduction. The effluent total and soluble chemical oxygen demand, total and volatile solids, and total Kjeldahl and ammonium nitrogen concentrations were significantly affected by the hydraulic retention time, air flow rate, and mixing speed. The system removal efficiencies were 15.90-58.61%, 25.20-69.33%, 12.43-49.90%, 9.22-51.77%, 1.66-10.06%, and 54.82-72.22% for total chemical oxygen demand, soluble chemical oxygen demand, total solids, volatile solids, total Kjeldahl nitrogen, and ammonium nitrogen, respectively, depending on the hydraulic retention time, air flow rate, and mixing speed used.     

Pollution potential reduction of cheese whey through yeast fermentation

Batch and continuous pilot-scale aerobic fermenters of 4.8 L operating volume were designed and constructed from plexiglass materials. The fermenters were used to study the kinetics of cheese whey fermentation using the yeast K. fragilis for pollution potential reduction and single cell protein production. Four retention times (6, 12, 18, and 24 h) were used in this study. The fermentation process was successful in reducing the total chemical oxygen demand (COD) by 42%, the soluble COD by 65%, the total solids by 53%, and the ammonium nitrogen by 90%. There were also gains in the suspended solids and the organic nitrogen of 60 and 17%, respectively. The reductions in the COD, total solids, and ammonium nitrogen, and the gains in the suspended solids and organic nitrogen were affected by the hydraulic retention time. More soluble material was converted to insoluble microbial cells at the 12-h hydraulic retention time, whereas greater pollution potential reduction was achieved at the 24-h hydraulic retention time for both batch and continuous operations.     

Utilization of cheese whey lactose by kluyveromyces fragilis for energy and growth under continuous fermentation

A heat balance was performed on a 25 L jacketed continuous stirred tank reactor used for the production of single cell protein from cheese whey usingKluyveromyces fragilis under three levels of retention time (12, 18, and 24 h), two levels of air flow rate (1 and 3 VVM), and three levels of mixing speed (200, 400, and 600 RPM) to determine the heat of reaction and the portions of lactose used for energy and growth as well as to assess the need for the cooling system. The yeast population size, oxygen concentration, and lactose concentration in the reactor as well as the portions of lactose used for energy and growth were all affected by the hydraulic retention time, mixing speed, and air flow rate. About 8-14% of lactose was utilized for energy and 86-92% was utilized for growth. The highest cell number was obtained at the 12 h retention time, 3 VVM air flow rate, and 600 RPM mixing speed. Under these conditions, the lactose removal efficiency was 95.6% and the yeast yield was 0.78 g cell/g lactose removed.     

一种EGA—MS系统的标定方法

ＣａＣ２Ｏ４真空热分解中，第一阶段生成的ＣＯ中４７％歧化成ＣＯ２和Ｃ；第二阶段生成的ＣＯ与第一阶段生成的Ｃ发生气化反应，发生反应的比例随样品量增加而增大。用ＣａＣＯ３标定ＣＯ后再用ＣａＣ２Ｏ４标定ＣＯ可以排除这些干扰。本文提出了一个对任意气体标定的方法。     

The effect of sodium sulfite and cobalt chloride on the oxygen transfer coefficient

An experiment was conducted in an aeration system made from 2000 mL Erlenmeyer Flask to investigate the effect of sodium sulfite with cobalt chloride and the sparging nitrogen gas on the measurement of the oxygen transfer coefficient. Twice the theoretical quantity of sodium sulfite that is required to react with dissolved oxygen, or nitrogen sparging at a rate equivalent to that of air used during the aeration process, was used to deoxygenate the water. The results obtained from the study were consistent and repeatable and showed no significant differences in the values of the oxygen transfer coefficient obtained by the two methods.     

Effect of pH control on the growth and survival ofKluveromyces fragilis in cheese whey under aerobic condition

Many biological and chemical systems involve acid-base equilibria and thus depend critically on the pH of the solution. Small fluctuations of pH must be corrected by the addition of an acid or base to maintain the pH at the required optimum level during the fermentation process. The effect of pH control on the growth ofKluveromyces fragilis, used for the production of single-cell protein from cheese whey, was investigated. Maintaining the pH at 4.5 was found essential for the survival of the yeast. Without pH control, the pH of the medium continued to rise, resulting in the death and/or sporulation of the yeast cells. Diauxic growth was observed, caused by the growth of contaminant bacteria when the pH was not controlled.     

Mixed convective heat and mass transfer in a non-Newtonian fluid at a peristaltic surface with temperature-dependent viscosity

We investigate the problem of the unsteady mixed convection peristaltic mechanism. The flow includes a temperature-dependent viscosity with thermal diffusion and diffusion-thermo effects. The peristaltic flow is between two vertical walls, one of which is deformed in the shape of traveling transversal waves exactly like peristaltic pumping and the other of which is a parallel flat plate wall. The equations of momentum, energy, and concentration are subject to a set of appropriate boundary conditions by assuming that the solution consists of two parts: a mean part and a perturbed part. The solution of the perturbed part has been obtained by using the long-wave approximation. The mean part has been solved and coincides with the approximation of Ostrach. The mean part (zeroth order), the first order, and the total solution of the problem have been evaluated numerically for several sets of values of the parameters entering the problem. The skin friction, and the rate of heat and mass transfer at the walls are obtained and illustrated graphically.