Diacetyl production mechanism by a strain ofLactococcus lactis spp.lactis bv.diacetylactis

Diacetyl production via alpha-acetolactic acid (ALA) extracellular decarboxylation inLactococcus lactis spp.lactis bv.diacetylactis SD 933 cultures has been assessed under anaerobiosis both in batch and continuous fermentations at pH 5.5 and 8.0 by studying the effects of alpha-acetolactate decarboxylase (ADC) addition in the culture broth. This enzyme, favoring the formation of acetoin instead of diacetyl, was added extracellularly and did not disturb diacetyl production. Moreover, oxidation experiments on extracellular culture media did not reveal any increase in diacetyl amount caused by extracellular ALA oxidative decarboxylation. These observations confirm previous assertions concerning the mechanism and localization of diacetyl synthesis by theSD 933 strain.     

In Situ Crystallization of Bacterial Cellulose III. Influences of Different Polymeric Additives on the Formation of Microfibrils as Revealed by Transmission Electron Microscopy

Effects of polymer additives on the formation of microfibrils of bacterial cellulose have been examined by transmission electron microscopy. Among additives with different degrees of polymerization (DP) or substitution (DS), carboxymethyl cellulose sodium salt (CMC) with DP = 80 and DS = 0.57 is the most effective in producing separate, smaller-size microfibrils. By increasing the concentration of this CMC from 0.1 to 1.5%, the percentage of microfibrils measuring 3–7 nm wide is increased and levels off at around 1.0%. Other polymer additives such as xyloglucan are less effective than CMC in producing microfibrils with smaller sizes and the resulting microfibrils still tend to aggregate. The number of charged substituents and the molecular weight seem to be important factors in the production of highly separate smaller-size microfibrils. The reduction in average microfibril size is well correlated to the decrease in mass fraction of cellulose I in bacterial cellulose crystals. On the basis of these results, the mechanism of the crystallization of celluloses I and I is discussed. The effect of colony types, smooth and rough, on the formation of microfibrils in the presence of CMC is also described.     

L—天冬门酰胺微生物电极的研制

以谷氨酸棒状杆菌作为生物催化剂，与基础氨气敏电极结合制成对Ｌ－天冬门酰胺响应的微生物电极，在３０℃时选择ＰＨ＝８．５的硼酸缓冲体系，测得电极的线性范围为７．１×１０＾－５－１．１×１０＾－２ｍｏｌ／Ｌ，斜率为５１．４ｍＶ／ｄｅｃ，检测下限为２．０×１０＾－５ｍｏｌ／Ｌ，响应时间为４－７ｍｉｎ寿命达３０ｄ以上。     

Sodium hydrogen dipicolinate dipicolinic acid trihydrate: Synthesis,structure, and valence bond sums

The synthesis and crystal structure of sodium hydrogen dipicolinate dipicolinic acid trihydrate, NaHdipic · H₂dipic · 3H₂O,I, is reported. There is a hydrogen bonded H₃(dipic)₂ ^– unit in which an Hdipic^– ion functions as a tridentate chelate to the Na⁺ ion while the second H₂dipic functions as a monodentate ligand and bridging unit. The Na⁺ ion is in the center of a pentagonal bipyramid with two water molecules in the axial positions. The equatorial plane is composed of an Hdipic^– ion, a water molecule and an oxygen from the H₂dipic. An analysis of data in the Cambridge Structural Database for Na⁺ compounds using Valence Bond Sums has produced newr ₀ values of 1.743 for Na–O and 1.891 for Na–N.     

Development of high-performance and rapid immunoassay for model food allergen lysozyme using antibody-conjugated bacterial magenetic particles and fully automated system

A high-performance and rapid chemiluminescence immunoassay for model food allergen lysozyme, one of the major allergenic components in egg white, using antibody-conjugated bacterial magnetic particles and a fully automated system was developed. This system contians a reaction station, tip rack, and an eight-tip pipettor that is alble to attach and detach a strong magnet to the tip surface. The immunoreaction time was shortened to 5 min, and the assay was completed within 20 min. The lower detection limit for lysozyme was 10 ng/mL. This system can be used to perform 24 samples in 60 min within 10% coefficient of variation.     

受周期外界环境影响的VanderPol情绪模型

本文以VanderPol方程为基础，建立了受周期外界环境刺激影响的非线性动态情绪模型，并在Matlab环境下实现了具有混沌性质的数值模拟，所建立的模型很好的模拟了情绪变化的规律，并为计算机实现智能化打下了基础。     

Saccharide‐Modified Nanodiamond Conjugates for the Efficient Detection and Removal of Pathogenic Bacteria

The detection and removal of bacteria, such as E. coli in aqueous environments by using safe and readily available means is of high importance. Here we report on the synthesis of nanodiamonds (ND) covalently modified with specific carbohydrates (glyco–ND) for the precipitation of type 1 fimbriated uropathogenic E. coli in solution by mechanically stable agglutination. The surface of the diamond nanoparticles was modified by using a Diels–Alder reaction followed by the covalent grafting of the respective glycosides. The resulting glyco–ND samples are fully dispersible in aqueous media and show a surface loading of typically 0.1 mmol g^?1. To probe the adhesive properties of various ND samples we have developed a new sandwich assay employing layers of two bacterial strains in an array format. Agglutination experiments in solution were used to distinguish unspecific interactions of glyco–ND with bacteria from specific ones. Two types of precipitates in solution were observed and characterized in detail by light and electron microscopy. Only by specific interactions mechanically stable agglutinates were formed. Bacteria could be removed from water by filtration of these stable agglutinates through 10 μm pore‐size filters and the ND conjugate could eventually be recovered by addition of the appropriate carbohydrate. The application of glycosylated ND allows versatile and facile detection of bacteria and their efficient removal by using an environmentally and biomedically benign material.     

P. M. R. Spectroscopic Analysis of Bacterial Polysaccharides Containing Pyruvic Acid

Abstract

The characteristic p.m.r. signal at τ 8.4–8.6 given by the CH₃-C group of a pyruvic acid ketal (1-carboxyethylidene derivative)may be used to demonstrate the presence of such a substituent in polysaccharides. Similar signals are given when the pyruvic acid ketal is methylated or reduced. The method is convenient for monitoring purification procedures and chemical transformations of polysaccharides such as are involved in structural studies. In certain cases the molar ratio of pyruvic acid may be estimated.