β-Casein will chaperone β-lactoglobulin during nanofibril assembly,but prefers familiar company at high concentrations

Bovine β-casein behaves as a chaperone at neutral pH, i.e., it inhibits aggregation of unfolded proteins, but chaperone effects have not been investigated at acidic pH. We examined chaperone effects during heating at pH 2 and 80 °C for mixtures of 1% (w/v) β-lactoglobulin (β-Lg) and β-Lg:β-casein molar ratios of 1:0.0625 to 1:1. These conditions hydrolyse β-Lg into peptides that self-assemble into amyloid-like nanofibrils. Hydrolysis rates in mixed solutions were unchanged from single-protein controls, according to sodium dodecyl sulphate polyacrylamide gel electrophoresis. At ratios ≥1:0.125, β-casein slowed fibril growth in a concentration-independent way, according to Thioflavin T fluorescence. We observed twisted irregular fibrils coexisting with long semiflexible fibrils when β-casein was heated with β-Lg, using transmission electron microscopy. We hypothesise that β-casein monomers and peptides can interact with growing β-Lg nanofibrils or assemble into micelles, with the latter pathway predominating at high β-casein concentrations.     

Effects of larval crowding and nutrient limitation on male phenotype,reproductive investment and strategy in Ephestia kuehniella Zeller (Insecta: Lepidoptera)

Food shortage experienced by juvenile insects affects adult morphology and life-history traits. Developmental plasticity and trade-off between ecological and sexual traits helps maximise individual fitness. Ephestia kuehniella were reared at different larval densities to investigate phenotypic shifts in adult males. Variation in ecological traits (sizes of forewing, head and thorax and adult longevity) and sexual traits (valva and aedeagus, sperm number, mating frequency) were compared. Males that emerged from highest density population (800) had lower body mass and small forewings, head and thorax, suggesting that they could not completely compensate for food shortage. The allometric relationship between body mass and forewing length also changed, and these males had relatively longer wings. This arrangement may enhance dispersal and assist in mate-searching at higher densities. Males from all larval densities achieved similar mating frequency but those from higher density produced fewer eupyrene sperm and had shorter adult lifespan. By mating more frequently and maintaining apyrene sperm production, males increase their reproductive success at sperm competition observed at higher densities. Food stress associated with high density populations did not affect valva and aedeagus size indicating that these traits may be insensitive to external environmental changes because they incur fitness costs to males.     

Sanitization potency of slightly acidic electrolyzed water against pure cultures of Escherichia coli and Staphylococcus aureus,in comparison with that of other food sanitizers

The sanitization potency of slightly acidic electrolyzed water (SAEW) on pure cultures of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) was evaluated. The potency was compared with that of strong acidic electrolyzed water (StAEW) and sodium hypochlorite (NaOCl) solution. SAEW (ca. pH 5.8 and 21 mg/l available chlorine concentration; ACC) resulted into >5 log₁₀CFU/ml reduction of E. coli and S. aureus after 90 s of exposure. The relative bacterial reduction potency at each exposure time was in the order StAEW > NaOCl > SAEW and increased with exposure time, with relative effect being 90 s > 60 s > 30 s. The results indicate that SAEW with low ACC and near neutral pH can potentially sanitize E. coli and S. aureus within a short period of exposure presenting a potential replacement to NaOCl solution commonly used in the food industry.     

结合感官评价与电子舌技术优化酶水解养殖暗纹东方鲀肌肉制备呈味肽

国内外关于河豚滋味的研究主要集中在游离氨基酸、无机离子、核苷酸及其关联物上,而对构成其鲜美浓郁和圆润香滑味感的呈味肽研究较少。因此应用酶生物技术挖掘滋味特性突出的暗纹东方鲀肌肉呈味肽,并应用于食品中具有重要的研究意义与潜在的经济价值。以养殖暗纹东方鲀肌肉为原料,采用中性蛋白酶、风味蛋白酶、水解蛋白酶及复合蛋白酶制备呈味肽,以水解度、寡肽含量和电子舌结合感官评价的方法筛选不同酶解条件下的最优酶制剂。结果表明:风味蛋白酶酶解液水解度最大而水解蛋白酶酶解液寡肽含量最高;电子舌能够明确区分出不同蛋白酶酶解液;电子舌分析结果与感官评价结果存在一定的相关性,但电子舌提供的鲜味、咸味和酸味相对强度与感官评定的结果存在一定的差异。最终确定中性蛋白酶为酶解暗纹东方鲀肌肉制备呈味肽最佳酶制剂。     

Biphasic calcium phosphate scaffolds fabricated by direct write assembly: Mechanical,anti-microbial and osteoblastic properties

The present work reports on the fabrication of 3-D porous calcium phosphate scaffolds by robocasting from biphasic (HA/β-TCP ≈ 1.5) powders, undoped and co-doped with Sr and Ag. Scaffolds with different pore sizes and rod diameter of 410 μm were fabricated and sintered at 1100 °C. The size and morphology of the powder particles, and the concentrations of the processing additives, were shown to play major roles in the robocasting process. For all pore sizes tested, the compressive strength of scaffolds was comparable to or even higher than that of cancellous bone, and mechanical data could be systematically correlated with the porosity fraction. Co-doping the starting powders with Sr and Ag enhanced the mechanical strength of scaffolds, conferred good antimicrobial activity against Staphylococcus aureus and Escherichia coli, and did not induce any cytotoxic effects on human MG-63 cells. Furthermore, the co-doped powder was more effective in inducing pre-osteoblastic proliferation.