辐照对黄原胶分子量、结构及流变性能的影响

 【目的】探讨辐照剂量对黄原胶分子量、分子量分布、结构、流变性能的影响,为辐照技术在黄原胶及其它多糖分子修饰上的应用提供理论依据。【方法】以60Co-γ射线对固态黄原胶进行不同剂量 (0—400 kGy) 的辐照,采用凝胶渗透色谱（GPC）、X-射线衍射(XRD)、红外扫描(FTIR)、紫外-可见光扫描(UV-vis)以及流变仪等对样品的分子量、分子量分布、结构以及流变性能进行表征和测定。【结果】低于10 kGy剂量的辐照使黄原胶分子量增大,分子量分布变窄;辐照剂量高于10 kGy后,分子量随剂量增大而降低,而分子量分布先变宽,在50 kGy时达到最大后,又趋于变窄。X-射线衍射、红外及紫外分析表明,辐照造成黄原胶分子上的部分糖苷键发生断裂,引起结晶度的变化,并在链端产生少量羰基,但其基本化学结构和晶体结构保持稳定。辐照处理后,黄原胶溶液的表观黏度与剪切速率、剪切时间和温度之间的关系均发生了显著变化。【结论】γ射线可同时作用于黄原胶的结晶区和无定形区,引发聚合和降解两种辐照效应,并对其分子量、分子量分布造成显著影响,进而使其流变性能发生改变。     

分散剂及黄原胶对多菌灵悬浮剂流变性质的影响

为探索不同分散剂与黄原胶对农药悬浮剂流变性质的影响,指导农药悬浮剂配方组份的选择,利用流变仪研究了两种不同分散剂与增粘剂对50%多菌灵悬浮剂流变性质的影响。结果表明,烷基酚聚氧乙烯磷酸酯类分散剂TERSPERSE4896、壬基酚聚氧乙烯醚类分散剂TERSPERSE2210与增粘剂黄原胶协同使用所得悬浮体系,室温(18~25℃)贮存10 d仍表现出二者共同的流变特性,呈假塑性的流变曲线;但室温贮存150 d 后,含TERSPERSE2210与黄原胶的悬浮体系的流变性质发生了明显变化,由假塑性流体向膨胀型流体转变。说明不同类型农药分散剂与黄原胶存在不同的协同作用,并且会直接影响农药悬浮剂体系的流变性能,从而影响农药悬浮剂的贮存物理稳定性。     

福建省脂松香质量调查与提高质量的建议

对连续15 a福建省脂松香生产企业的质量抽检调查及统计分析结果表明,各个级别脂松香质量的各项主要技术指标均优于目前的国家标准(GB/T 8145—2003)要求,但仍存在影响脂松香质量的问题。要通过实施松香全过程质量控制,并加快品牌创建,不断满足市场对产品质量的多样化要求,以提高松香产品质量与效益。     

黄秋葵食用胶的制备及应用研究进展

介绍了黄秋葵食用胶的组成、基本特性、制备及其在食品工业中和其他工业中的应用。     

地毯草黄单胞菌分泌黄原胶的电镜观察

为了研究地毯草黄单胞菌(Xanthomonas axonopodis)FJAT-10151产黄原胶的分泌行为,采用比浊法测定地毯草黄单胞菌的生长曲线,干重法测定黄原胶产量,2,4-二硝基苯肼显色法测定黄原胶中丙酮酸含量变化,通过扫描电子显微镜镜(SEM)和透射电子显微镜镜(TEM)观察地毯草黄单胞菌产黄原胶的分泌行为。FJAT-10151在发酵时间0～26 h为对数期,26～72 h为稳定期。菌株FJAT-10151为短杆状(约2μm),端生鞭毛(约7.9μm),菌体外面形成了一层较厚的荚膜,且许多菌体通过黄原胶连在一起,分泌的黄原胶呈棒状和网状2种形态,聚集或缠绕在细胞表面,其含量随发酵时间的延长而增加。菌株FJAT-10151发酵72 h可获得高品质黄原胶,其产量及丙酮酸含量最高。     

Improving the mechanical characteristics of faecal waste in rainbow trout: the influence of fish size and treatment with a non-starch polysaccharide (guar gum)

This study (3 × 2 randomized factorial design) describes differences in the mechanical properties of faeces from rainbow trout of three size classes (small ≈40 g, mid-size ≈150 g, large ≈650 g) and assesses the effects of a non-starch polysaccharide binder (guar gum). Observations made at the macroscopic level were reinforced by rheological measurements of viscosity and elastic modulus. Mid-sized fish excreted mechanically the most stable faeces, roughly twice as stable as those of small fish and three times more stable than faeces from large fish. The addition of 3 g kg⁻¹ of guar gum saw some mechanical characteristics improve by about 700%. Faeces from large- and mid-sized fish were more easily stabilized than those of small fish. Mechanical recovery potential for faecal samples disrupted by water turbulence was determined. Stability differences observed for different fish size had no significant effect but the improvements imparted by guar gum reduced postfiltration effluent load to about 35% for large fish, about 24% for mid-size and about 22% for small fish. Faecal leaching decreased significantly with increasing stability. Guar gum was shown to have significant potential for improving the treatability of fish faecal waste.     

野油菜黄单胞菌重组克隆pIXU9278对黄原胶生物合成的影响

用ＰＩＪ３２００作为载体,构建了包含１５６２个重组克隆野生型野油菜黄单胞菌的粘粒文库,通过三亲交配法,基因文库中的重组克隆可以在ＰＲＫ２０１３的帮助下,从Ｅ．ｃｏｄｉ中以ＸＣＣＮＡＵ－９２中,绝大多数重线克隆对黄原胶合成无影响,但导致菌株生长缓慢,工程菌株ＸＣＣＮＡＵ－９２７８（ＰＩＸＵ９２７８）在２８℃、１２０ｔ／ｍｉｎ条件下发酵７２ｈ,产量达３７．５０ｇ／ｋｇ,发酵液度力为１４６００ｍＰａ．ｓ     

地毯草黄单胞菌发酵生产黄原胶工艺条件优化

为了获得更高品质的黄原胶,优化黄原胶高产菌株地毯草黄单胞菌FJAT-10151的发酵工艺,通过单因素及正交设计对培养基(碳源、氮源和无机盐离子)和发酵条件(发酵时间、pH、装液量和接种量)进行优化,试验获得最佳发酵培养基为葡萄糖30g·L~(-1)、豆饼粉30g·L~(-1)、KH2PO42g·L~(-1)、pH值9.0。在装液量50mL/250mL、接种量8%培养条件下发酵72h,黄原胶产量达到21.0g·L~(-1),是初始培养条件产量8.65g·L~(-1)的2.43倍。优化发酵工艺后,黄原胶品质提高,丙酮酸含量从8.9%升高到16.3%,而蛋白质含量从15.27%降低到4.8%。     

Clear increases in acetylene reduction by soil bacteria from an East Siberian Taiga forest bed under conditions mimicking the natural soil environment

Abstract

In boreal forest ecosystems, nitrogen imbalance has long been discussed as a mystery with regard to its high biomass production. Under conditions widely used for the soybean nodulation bacterium Bradyrhizobium japonicum, microbiota in forest bed soil often do not show any significant acetylene reduction. However, in a recent study, soil bacterial microbiota in an East Siberian Taiga forest bed and bacteria isolated from the soil show remarkable acetylene reduction in nitrogen-poor soft-gel medium solidified with gellan gum instead of agar. Thus, we precisely investigated optimal culture conditions including compositions of the medium; appropriate conditions for the soil microbiota were determined as follows: 0.5 g L^?1 D-mannitol as the carbon source, 10–15°C incubation temperature and medium pH 6.2. These culture conditions resembled the physicochemical conditions of the active layer in the East Siberian boreal forest bed on the permafrost. In fact, mannitol, which was the most appropriate carbon source, was obtained as a major sugar component of the cowberry root mats that cover the larch forest bed in this region. The most profitable concentration of D-mannitol (0.5 g L^?1) for acetylene reduction was only 1/20 or 1/30 of the amount of the carbon source used in worldwide acetylene reduction assays. In a similar manner, 10–15°C, which was the most profitable incubation temperature range, was close to the reported temperature of the active layer of the bulk soil in summer. us, even in a 3.0 g L^?1 gellan gum medium, an acetylene reduction assay under the imitated soil conditions led to clear increases in acetylene reduction of the bacterial communities tested. The N₂-fixing potential of boreal forest bed soil had thus ever been evaluated unfairly low, because the world wide assay conditions were too far from the soil environments.     

魔芋胶酶解工艺条件的优化

[目的]探讨在中试条件下利用中性β-甘露聚糖酶水解魔芋胶制备低聚甘露糖的工艺条件。[方法]在单因素试验条件下,研究了利用枯草芽孢杆菌所产生的中性β-甘露聚糖酶对魔芋胶进行水解来制备低聚甘露糖的工艺条件。[结果]酶法水解魔芋胶生产低聚甘露糖时,优化的酶解条件为：pH6.0,魔芋胶浓度125g/L,酶量200IU/g魔芋胶,酶解温度50℃,酶解时间3h。[结论]该研究可极大地提高魔芋胶的附加值。