Whey protein membrane processing methods and membrane fouling mechanism analysis.

Whey is a byproduct with nutritional value and high organic and saline content. It is an important source of organic contamination in dairy industry. In this paper, we gave an overview of the current use of membrane materials and membrane processing in cheese whey protein recovery and discussed recent developments in membrane technology. Different types of membranes, such as polymers, ceramic membranes and modification membranes, are used for various purposes, such an increasing permeation flux, reducing membrane fouling, and increasing the protein rejection rate, concentration, fractionation and purification of whey protein. New membrane processing methods and integrated membrane methods to recover whey protein were reviewed. Membrane fouling factors during whey protein ultrafiltration process, which included whey protein conformation, membrane filtration conditions and the interaction between proteins and the membrane surface or pores, were also discussed and analyzed to reveal membrane fouling mechanism.

Optimization of transglutaminase (TG) immobilization on the surface of polyethersulfone ultrafiltration membrane and its characteristics in a membrane reactor.

The process of microbial transglutaminase (TG) covalent immobilization on an ultrafiltration membrane surface, the optimum immobilization conditions and the characteristics of the enzymatic membrane in a reactor were investigated. The process of TG immobilization on polyethersulfone (PES) membrane surfaces was analyzed by Fourier transform infrared and X-ray photoelectron spectroscopy. The optimal condition for TG immobilization was in pH 5.0 phosphate buffer containing TG (20 U/mL). The immobilized TG had a high affinity for the substrate according to the kinetic parameters and retained 50% activity until the twentieth day. Water contact angle and antifouling tests showed that the hydrophilicity of immobilized-transglutaminase membrane was improved compared with pure PES membrane. The enzyme could maintain relatively high activity under a transmembrane pressure of 0.15 MPa. Moreover, the enzymatic membrane had higher relative membrane flux at 0.15 MPa in a membrane reactor, and could retain its activity in pH 5.0 phosphate buffer and catalysis under 40 °C.

Di (n-butyl) phthalate inhibits testosterone synthesis through a glucocorticoid-mediated pathway in rats.

The present study focused on investigating whether the inhibitory effect of di (n-butyl) phthalate (DBP) on testosterone (T) biosynthesis was mediated by the glucocorticoid (GC) pathway in prepubertal male rats and T production after the exposure to DBP ceased. Prepubertal male rats were administered DBP in corn oil orally at 0, 250, 500, 1000, and 2000 mg/kg daily for 30 days. Serum T and GC were measured by radioimmunoassay and enzyme-linked immunosorbent assay, respectively. The responses, including glucocorticoid receptor (GR), type I 11beta-hydroxysteroid dehydrogenase (11beta-HSD1), and steroidogenesis acute regulatory protein (StAR) in the testes tissues, were determined by Western blotting and reverse transcriptase PCR. DBP exposure resulted in testicular toxicity, such as seminiferous tubule degeneration and a decrease in the number of spermatogenic cells. T was decreased and GC was increased in a DBP concentration-dependent manner in the exposure group. The expression of GR and 11beta-HSD1 was significantly increased, with an associated decrease in expression of StAR. Neither the expression of the GR nor 11beta-HSD1 and StAR were statistically significantly different in the postexposure group compared with the control. However, the weight and morphology of the testes did not recover in the postexposure group. These data suggest that DBP inhibits testosterone production through a GC-mediated pathway in prepubertal male rats, and after exposure to DBP ceases, testosterone biosynthesis returns.