果胶性能的研究——[Ⅰ].果胶与 Cu~(2+)Pb~(2+)和 Fe~(3+)离子反应

本文着重研究果胶与 Cu~(2+)、pb~(2+)和 Fe~(3+)离子反应的规律.实验表明,在一定条件下(温度、pH 等),果胶与这些金属离子反应的定量关系为:每克Cu~(2+)、pb~(2+)和 Fe~(3+)离子能够分别与30.86g、13.20g 和86.64g 的果胶(P-1)完全反应生成沉淀.本文还就温度、pH 和时间等条件对上述反应的影响进行了初步的探讨.     

九种金属离子对桑椹红色素稳定性影响的研究

本文报道Fe~(2+),Fe~(3+)……Ca~(2+)等9种金属离子对桑椹红色素稳定性影响的研究。结果表明:Fe~(2+),Fe~(2+),Cu~(2+),Zn~(2+)对该色素颜色的稳定性有不利影响;Mg~(2+),Al~(3+),K~+,Na~+,Ca~(2+)等5种金属离子有增强其吸收值的作用,其中Al~(3+)增色作用最为明显,Ca~(2+)护色作用较为突出,但它们的作用都随时间延长而逐渐降低。     

响应面法优化Fe~(2+)的微生物氧化条件

氧化亚铁钩端螺旋菌(Leptospirillum ferrooxidans,L.f)是一种极端嗜酸,专性自养氧化铁的细菌,能够耐受较低pH和较高的温度,被广泛应用于生物浸矿和环境治理。氧化亚铁钩端螺旋体菌的生物浸矿效率与其对Fe~(2+)氧化速率相关,因此,本文采用响应面法,通过建立二次多项式回归方程考察pH、温度、Fe~(2+)浓度及转速四个培养因素对Fe~(2+)氧化速率的影响。结果显示在pH为2.25、温度为32℃、初始Fe~(2+)浓度为175.36 mmol/L、转数为165 r/min时,Fe~(2+)最高氧化速率为0.2911 g/Lh。     

粒毛盘菌黄色素的稳定性研究

【目的】评价粒毛盘菌黄色素的稳定性。【方法】以色素吸光值为指标,研究温度、光照、pH、金属离子、氧化剂、还原剂及食品添加剂对黄色素稳定性的影响。【结果】该黄色素属黄酮类物质,易溶于水,在水溶液中紫外区及可见光区各呈现一个吸收峰,最大吸收波长分别为300 nm和410 nm;热稳定性较好,70°C处理4 h的色素保存率近90%;光照能降低黄色素水溶液的稳定性;随着pH的升高,色素溶液颜色逐渐加深,其A410增大;色素溶液在pH 9.0-10.0下较稳定,pH 10.0的色素溶液放置5 d后色素保存率近90%;Na_2SO_3对色素水溶液有增色作用,色素水溶液抗NaNO_2、H_2O_2能力较强,对抗坏血酸敏感。Fe~(3+)、Fe~(2+)与色素反应而改变色素颜色,Al~(3+)、Cu~(2+)、Zn~(2+)对色素水溶液具有一定的褪色作用,Ca~(2+)、K~+、Mg~(2+)对色素溶液无明显影响。蔗糖、葡萄糖和山梨酸钾对色素水溶液无明显影响,氯化钠对色素水溶液具有较弱的褪色作用。【结论】粒毛盘菌黄色素在稳定性上呈现出一定优势,具有开发潜力。     

不同浓度Fe~(2+)和Cu~(2+)胁迫对灵芝寡肽转运蛋白基因家族的转录表达水平的影响

前期研究发现在Fe~(2+)和Cu~(2+)胁迫下,OPT基因转录表达水平会有较大的变化。为进一步探究这两种金属对OPT基因的影响,分析了不同浓度Fe~(2+)和Cu~(2+)胁迫下灵芝寡肽转运蛋白基因家族的转录表达水平。以灵芝荣保1号为实验材料,设置不同浓度梯度(0、50、100、200和400 mg/L)Fe~(2+)和Cu~(2+)进行液体静置培养,分别于15 d和30 d收集样品,测定生物量和多糖含量,利用实时荧光定量PCR技术分析OPT基因的转录表达水平。结果表明,Fe~(2+)对灵芝的生长有一定的促进作用,Cu~(2+)则对其有抑制作用。两种金属在实验用的浓度范围内对于灵芝多糖含量在培养前期表现出抑制作用,后期则有一定的促进作用。除未检测到转录本的3个OPT基因(OPT7、OPT8和OPT9),其余OPT基因的转录表达均有差异性。培养前期(15 d),Cu~(2+)胁迫下OPTs基因表达水平较低且差异不明显,Fe~(2+)胁迫下OPTs基因表达水平差异较大;培养后期(30 d),Cu~(2+)胁迫下OPTs基因表达水平较15 d的样品明显增加,且存在差异,Fe~(2+)胁迫下绝大多数OPTs基因均在浓度为200 mg/L下转录表达水平最高。实验证明,不同浓度Fe~(2+)和Cu~(2+)对灵芝的生物量与多糖含量存在不同程度的影响,同时OPT基因在转录水平上也做出了不同的响应,表明其在灵芝适应与吸附外界金属离子的过程起到了重要的作用。     

青藏高原黑果枸杞花青素稳定性评价

采用控制变量法分别研究了环境因素(pH、温度、光照)和添加物(氧化剂、还原剂、食用酸、糖、防腐剂和金属离子)对青藏高原黑果枸杞花青素稳定性的影响。用分光光度计法测定花青素含量的变化。结果表明,酸性(pH3)、低温(T60℃)、避光条件有利于花青素溶液稳定保存。氧化剂(H_2O_2)和还原剂(Na_2SO_3)对花青素稳定性有不良影响;食用酸(柠檬酸、抗坏血酸、草酸、酒石酸)、葡萄糖、蔗糖可增加花青素稳定性;防腐剂苯甲酸对花青素稳定性无显著影响;金属离子Na~+、K~+、Ca~(2+)、Mg~(2+)、Al~(3+)对花青素稳定性无不良影响,而Zn~(2+)、Cu~(2+)、Fe~(3+)对花青素稳定性有不良影响。     

一株黑果枸杞内生真菌RML6的黄色素稳定性研究

植物内生真菌具有产天然活性物质的潜能,亦是天然色素的来源之一,本研究从黑枸杞叶部分离筛选得到产黄色素的内生真菌RML6,经鉴定该菌为Coprinellus radians,该菌株所产黄色素在341 nm波长处有最大吸收峰。从温度、pH、光照、金属离子、氧化剂与还原剂等方面探究黑枸杞内生真菌RML6所产黄色素的稳定性。结果表明该色素在自然光下放置8 h黄色素光吸收值无显著变化,但对紫外较为敏感应尽量避光存放;在pH 6~10,20~100℃下不受太大影响;金属离子中,Na~+、K~+、Mg~(2+)、Cu~(2+)、Fe~(3+)对该色素有护色或增色作用,Zn~(2+)、Mn~(2+)、Ca~(2+)对色素有明显的影响;H_2O_2、NaHSO_3对该色素有较强的破坏力;常见几种添加剂对色素无太大影响,同时蔗糖对其还具有明显的增色效应。该色素可广泛用于多个用途。     

中温碱性脂肪酶的研究——Ⅲ.扩展青霉PF868变株碱性脂肪酶的纯化及其酶学性质

扩展青霉PF868变株发酵液经硫酸铵盐析和Sephadex-G-200及Sepharose4B柱层析纯化,获得纯化倍数为32.4的酶粉.该酶分子量为23442Dal.酶学特性表明:该酶的最适作用温度为32℃,50℃保温30min仍保留50%酶活性,最适pH为9.0,作用pH稳定范围在7.0—10.0之间.Ca~(2+)Mg~(2+)对酶有激活作用.Fe~(2+)、Cu~(2+)和Mn~(2+)对酶活力有抑制作用.     

类产碱假单胞菌耐热碱性脂肪酶的研究

从福建省福州市温泉澡堂污水浸润土壤中分离筛选到一株耐热碱性脂肪酶产生菌——类产碱假单胞菌(Pseudomonas pseudoalcaligenes)F331。产酶最适条件为:碳源小麦粉,氮源豆饼粉,起始培养pH9.4～9.5,培养温度24～26℃,培养周期32～34h。经硫酸铵盐析、Sepharose 4B和Sephadex G-200柱层析得到纯化的酶组分。该酶最适作用温度50℃,最适作用pH 10.0,60℃保温80min酶活基本不损失,在pH 7.0～10.0范围内酶蛋白稳定:Ca~(2+)和Mg~(2+)对酶有激活作用,Pb~(2+).Zn~(2+)、Fe~(2+)和Co~(2+)对酶活有抑制作用。该酶分子量45700。     

新型海洋源β-半乳糖苷酶在毕赤酵母中的表达与酶学性质

从海洋环境β-半乳糖苷酶基因出发,采用毕赤酵母表达体系,构建产β-半乳糖苷酶的基因工程菌,并对重组酶酶学性质进行表征。结果发现:海洋源β-半乳糖苷酶具有优良的乳制品用酶特性,该重组酶的最适pH为7.0~8.0,最适温度为45℃,在50℃以下孵育1 h可保持55%以上的活力,能耐受Fe~(2+)、Na~(2+)、K~(2+)、Ca~(2+)等多种金属离子。宽广的pH、温度、金属离子稳定性,以及低温活性赋予该酶良好的乳制品用酶特性。     

Effect of hydroxyl radical on the scission of cellular wall polysaccharides in vitro of banana fruit at various ripening stages

Fruit ripening is generally attributed to disassembly of cellular wall, particularly due to solubilisation and depolymerisation of pectin and hemicellulose. Experiments were conducted to test effects of hydroxyl radicals (·OH) on the scission of cellular wall polysaccharides from pulp tissues of banana fruit at different ripening stage. Cellular wall materials were isolated from pulp tissues of banana fruit at different ripening stages. Two pectic fractions, water soluble pectin (WSP) and acid soluble pectin (ASP), and two hemicellulosic fractions, 1 M KOH soluble hemicellulose (HC1) and 4 M KOH soluble hemicellulos (HC2), were obtained from the cellular wall materials from pulp tissues, respectively. Effects of ·OH induced by the Fenton reaction on the scission of pectin and hemicellulose in vitro were investigated. As fruit ripening progressed, the sugar components of the WSP, HC1 and HC2 attacked by ·OH showed obvious molecular-mass downshifts. Thus, ·OH caused the disassembly of polysaccharides (WSP, ASP, HC1 and HC2) from cellular walls of pulp tissues of banana fruit, demonstrated by the reduced molecular mass distribution. Moreover, ·OH production in pulp tissues increased significantly as banana fruit ripened, which further help account for the role of ·OH in accelerated fruit ripening.     

Evaluation of filamentous fungi and inducers for the production of endo-polygalacturonase by solid state fermentation

Aspergillus oryzae CCT 3940, Aspergillus awamori NRRL 3112 and a Trichoderma sp.) were compared for their capacity to produce endo-polygalacturonase (endo-PG) in solid state fermentation. Maximum pectinolytic activity was reached in 72 h of growth, the best two fungal strains being A. niger T0005007-2 and A. oryzae CCT 3940. Three types of commercial purified pectin and four of unprocessed pectin (tangerine, orange, Tahiti lime and sweet lime rind) were used to assess the effect of pectin on the production of endo-PG by A. niger T0005007-2. Maximum pectinolytic activity was achieved using 6 and 10% (w/w) of purified pectin as inducer. Depending on the origin of the commercial pectin used as inducer, maximum endo-PG levels varied from 223 to 876 units per gram of dry medium (one endo-PG unit (U) was defined as the quantity of enzyme which caused a reduction in viscosity of 50% in a 1% w/v solution of pectin in 30 min), indicating that care should be taken when choosing this component of the medium. When the crude pectins were used as inducers at the same concentration as purified pectin, maximum endo-PG activities were 250-300 units/g. However, by increasing the amount of Tahiti lime rind to 50% (w/w) maximum endo-PG was 919 U/g, thus opening up the possibility of a low cost medium for endo-PG production.     

Purification and Characterization of an Endopolygalacturonase Produced by Sclerotinia Sclerotiorum

An endopolygalacturonase (endo-PG), was purified from the culture medium of a local isolate of Sclerotinia sclerotiorum with ammonium sulphate precipitation, cation exchange chromatography and gel filtration. The purified endo-PG had a molecular mass of approximately 18 kDa estimated by gel filtration. The isoelectric point was determined by isoelectric focusing to be approximately 8, suggesting that PG II possesses a net positive charge at physiological pHs. The pH optimum for the enzyme was at pH 4.5. The endo-PG showed essentially the same affinity for pectin and polygalacturonic acid as substrates. This revised version was published online in July 2006 with corrections to the Cover Date.     

Studies on Pectolytic Enzymes of Molds

Experiments have been made on fractionation of the pectolytic enzymes produced by Coniothyrium diplodiella. It has been observed that 30 to 35% of the polygalacturonase (PG) activity of the pectolytic enzymes of the said microorganism is salted out with ammonium sulfate, and this portion contains cndo-PG I, endo-PG II and pectin esterase (PE) (with a trace of exo-PG). The endo-PG I accounts for 60 to 65% of the total PG activity, and the endo-PG II, 25 to 30%. Both types of endo-PG scarcely act on pectin, and hydrolyze pectic acid to the extent of 65 to 70%.     

Pectinases in Aqueous Extracts of Ditylenchus dipsaci

Aqueous extracts of a population of Ditylenchus dipsaci isolated from onion and maintained monoxenically on onion callus contained endo-polygalacturonase (endo-PG) and endo-pectinmethyltranseliminase (endo-PMTE). In viscometric tests pH 4.2 and 4.0 were optimal for degradation of sodium polypectate and pectin N.F., respectively, by endo-PG. Endo-PMTE reduced viscosity of pectin N.F. optimally at pH 8.5 or above. Activity was dependent on CaCl₂. Pectinmethylesterase activity was not detected in water, NaCl, or sucrose extracts of these nematodes. The extracts macerated potato tuber tissue, onion cotyledonary tissue, and strips of onion epidermis from the ventral surface of onion bulb scales at pH 4.2, 5.3, and 6.2. Pectin could not be localized with hydroxylamine-ferric chloride reagent in macerated tissues treated for 24 hr with active extract.     

Extraction, partial characterization and bioactivity of polysaccharides from boat-fruited sterculia seeds

Three polysaccharides (water-soluble (WSP), alkali-soluble (ASP) and insoluble (IMP)) from boat-fruited sterculia seeds were obtained using different extraction methods. Moisture, ash, protein and total carbohydrate content of WSP, ASP and IMP were analyzed. WSP was rich in glucose, rhamnose, arabinose and galactose while small amount of xylose was also detected. The monosaccharide composition as well its relative content for WSP and ASP were similar. The intrinsic viscosity results demonstrated that ASP had much lower intrinsic viscosity than WSP, indicating partial polysaccharides were degraded into low molecular weight polymers during alkaline extraction. The acute anti-inflammatory bioactive results of polysaccharides indicated that WSP demonstrated an inhibitive effect toward acute inflammation.     

Endo-polygalacturonase production from untreated lemon peel byAspergillus sp. CH-Y-1043

Summary Endo-polygalacturonase (endo-PG) production byAspergillus sp. CH-Y-1043 using untreated lemon peel as the sole carbon source was investigated. This strain was observed to produce more activity of endo-PG at 37°C than at 29°C. Untreated lemon peel proved to be a beeter substrate than citrus pectin for endo-PG production. Modification of the culture medium and lowering of the initial pH to 2.8 caused a 10-fold increase in the production of endo-PG activity using lemon peel.     

Studies on Pectic Enzymes of Microorganisms

Conditions for the production of endo-polygalacturonase (endo-PG) with Aspergillus saitoi IAM 2217 in the submerged culture was examined. This strain was selected as the most potent producer of endo-PG. Endo-PG of this strain was produced in the absence of pectin, but the addition of pectin increased endo-PG activity when inoculated with proliferated mycelia.

As far as examined with a modified Czapek medium (ordinary constituents + pectin and ammonium tartrate), the addition of organic nitrogen sources, such as corn steep liquor, markedly reduced the enzyme producibility. As for the carbon and nitrogen amount in the medium, sucrose: 4%, pectin: 2%, NaNO₃: 1.15%, C/N = 10, gave the best result among tested.     

香蕉果实成熟软化过程中细胞壁物质的变化

系统研究了香蕉果实软化过程中细胞壁物质―醇不溶性固形物(AIS)以及3种不同性质的果胶物质:水溶性果胶(WSP)、酸溶性果胶(HP)和碱溶性果胶(OHP)含量的变化。结果表明:随果实的成熟软化,AIS的含量不断降低,且在呼吸跃变时急剧降低;WSP的含量不断增加,HP和OHP的含量不断减少,且均表现出在早期变化量少,在果实硬度迅速降低时变化明显。该研究进一步证明细胞壁物质的变化是导致香蕉果实软化的主要原因。