Chromium (VI) reduction in activated sludge bacteria exposed to high chromium loading: Brits culture (South Africa)

A mixed-culture of bacteria collected from a wastewater treatment plant in Brits, North-West Province (South Africa) biocatalytically reduced Cr(VI) at much higher concentrations than previously observed in cultures isolated in North America. Cr(VI) reduction rate up to 8 times higher than the rate in previous cultures was achieved by the Brits culture under aerobic conditions. Near complete Cr(VI) reduction was observed in batches under initial concentrations up to 200 mg Cr(VI)/L after incubation for 65 h in aerobic cultures. Under anaerobic conditions up to 150 mg Cr(VI)/L was completely removed after incubating for 130-155 h. In the previous cultures, complete removal was only achieved in cultures at an initial Cr(VI) concentration lower than 30 mg/L after incubation for 96-110 h. Consortium cultures were characterised using 16S rRNA partial sequence analysis. Results showed that the Gram-positive Bacillus genera predominated under aerobic conditions with a small composition of the Gram-negative Microbacterium sp. More biodiversity was observed in anaerobic cultures with the marked appearance of Enterococcus, Arthrobacter, Paenibacillus and Oceanobacillus species. Experiments run on purified individual species did not achieve the same level of Cr(VI) reduction as observed in the original consortium from sludge indicating possible existence of interspecies interactions necessary for optimum Cr(VI) reduction. All Cr(VI) reduced was accounted for as Cr(III) with a small error range (2-6%).     

Growth characteristics of a Bombyx mori insect cell line in stationary and suspension cultures

The growth characteristics of the BM-5 insect cell line of Bombyx mori (silkworm) have been experimentally investigated in order to develop optimal growth protocols when these cells are used to produce large quantities of biopesticides or human proteins by recombinant baculoviruses. Experiments were performed in 2 mL wells and 200 mL spinner flasks. Spinner flasks were operated at 80 rpm with 0.3% methyl cellulose (MCL) added to the medium in order to protect the cells from liquid shear stress. In addition to the effect of agitation rate and amount of MCL added to the medium, the cell response during the adaptation to growth in suspension from stationary cultures is reported. Exposure of the cells to varying nutrient and metabolite concentrations is accomplished through batch and repeated-batch modes in 2 mL wells. The results imply that glutamine is a limiting nutrient and lactate has an inhibitory effect on cell growth. Ammonia depletion from the medium was accompanied by uric acid accumulation, suggesting that ammonia is converted to this metabolic product by the “uricotelic” and “nucleicolytic” metabolic pathways.     

Transformation of Reichstein's compound S into prednisolone by immobilized mixed cultures

Reichstein's compound S was transformed into prednisolone in a single-step fermentation using immobilized mixed cultures, entrapped in different gels or adsorbed on clay particles. Calcium alginate at a gel concentration of 2% gave the highest transformation activities and prednisolone yields. The entrapped mixed cultures could be repeatedly used in batch-wise transformation for at least six times when suspended in diluted nutrient medium and for three times when suspended in distilled water; in the latter case the entrapped cultures required to be reactivated in nutrient medium for further reuse. Mixed cultures adsorbed on clay particles were successfully reused 18 times, with reactivation after the 9th and 15th uses. Continuous transformation of substance S into prednisolone by mixed cultures adsorbed on clay particles was more efficient than batch-wise reused adsorbed cultures and was dependent on the daily working medium volume.     

Assessment of inhibitory potency of antibiotics by MRI: apparent T 2 as a marker of cell growth

A new method to assess the antibiotic potency by MRI has been developed. Correlating ¹H NMR spectra of bacterial cultures with the extracellular parameters T ₂, OD₆₀₀, and pH, a relationship between cell growth and T ₂ variations was established. T ₂ is influenced by chemical exchange that depends on pH, composition, and concentration of the medium. Changes in the medium from bacterial metabolism are reflected in alternating T ₂ values. At 17.6 T, growth curves based on T ₂ values were measured simultaneously of several cultures of Streptococcus vestibularis. From T ₂ growth curves in the presence of varying concentrations of vancomycin, the minimum inhibitory concentration of the antibiotic could be determined to be 0.33 ± 0.08 μM. This value was in good agreement with the result obtained by the conventional broth microdilution. In principle, T ₂ growth curves can be determined on a large number of cultures simultaneously and may potentially be used as a novel tool in high through-put screening of novel anti-infective substances.     

Behaviour of the constitutive biota of two types of Spanish dry-sausages ripened in a pilot-scale chamber

The behaviour of the constitutive biota in eighty four samples belonging to two different types of Spanish dry-cured sausages during the ripening process in a pilot-scale chamber was investigated. Samples were analyzed in three stages during production: fresh product, first drying stage and finished product. Lactic acid bacteria (LAB) and Coagulase-negative cocci (CNC) were identified by the API system. In general, evolution of LAB and CNC during the ripening process of Spanish dry-cured sausages increased during the first days after which numbers of these organisms remained stable. Pediococcus pentosaceus and Staphylococcus xylosus, were the dominant species. Lactobacillus plantarum, Staphylococcus saprophyticus Staphylococcus simulans and Kocuria varians were also present. The results obtained show that the ripening process in a pilot-scale chamber under controlled conditions contributes to a more homogeneous behaviour of the constitutive biota, in comparison with commercial production standards.     

Enzymatic Cell Isolation and Explant Cultures of Rat Calvarial Osteoblast Cells

1Introduction Osteoblastcellsplayakeyroleintheformation,se cretionandmineralizationoftheextracellularmatrixof bonetissues[1,2].Thesecellssynthesizeandreleasebone matrixandglucoprotein,andhelpthematrixcalcifiedto formbones[3].Osteoblastcellculturetechnique…     

复合菌剂对发酵肉制品理化及生物学特性影响的研究

以自然发酵为对照,系统研究了人工接种复合菌剂对特定肉制品理化及生物学特性的影响.结果表明,发酵0～5 d的试验组肉制品pH及水分含量的下降速度较对照组迅速(P<0.05),乳酸菌和葡萄球菌为其优势菌群,且pH和水分含量的变化与乳酸菌和葡萄球菌数量的增减具有一定的相关性;试验组肉制品的色泽明显优于对照组;发酵结束时两种肉制品的硬度、咀嚼性、回复性均增大,而弹性降低;试验组肉制品的氨基酸和多不饱和脂肪酸含量较对照组有明显提高;试验组肉制品的过氧化值(POV)和硫代巴比妥酸值(TBAV)均显著低于对照组(p<0.05).数据显示,采用复合菌剂生产的肉制品的理化及生物学特性明显优于自然发酵的肉制品.     

高职院校国际合作学院特色文化建设初探

阐述了国际合作办学的现状,分析了儒家文明与西方文明,集体主义与个人主义,重农轻商与重商轻农的中西文化差异。提出通过建立正确的思想道德体系、引导学生健康成长,坚持民族文化尊严、吸收西方文化精髓,培养学生正确的价值取向、实现人生的自我价值,建立健全文化交流的新机制、培育祈通中西的人文情怀等途径,构建兼容并蓄、汇通中西的国际合作学院特色文化体系。