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1.
目的从云南豆豉样品中筛选产β-半乳糖苷酶的乳酸菌,并对其产酶条件进行研究。方法从云南省元阳、红河、建水、石屏等地采集豆豉样品,并从中分离得到355株微生物。结果经明胶诱导、脱脂乳平板实验,复筛得到87株蛋白酶产生菌,从中筛选产β-半乳糖苷酶的乳酸菌。通过X-Gal平板实验,共获得34株产β-半乳糖苷酶菌株,通过酶活测定,最终筛选得到1株高产β-半乳糖苷酶菌株GJ-1-3L,经16S rDNA序列分析鉴定为短乳杆菌;GJ-1-3L在以葡萄糖为碳源、多聚蛋白胨为氮源、起始pH 6.5的MRS培养基中,接种量为4%,35℃发酵培养12 h,其β-半乳糖苷酶活性高达6.73 U/mL,Cu2+、Ba2+对酶活有抑制作用,而K2HPO4、MgSO4则能促进酶活。结论 GJ-1-3L菌株来源于豆豉,能够产生β-半乳糖苷酶发酵乳糖,同时产生乳酸,其在食品与乳品加工等方面具有很好的应用前景。  相似文献   

2.
【背景】低温β-半乳糖苷酶能在低温下仍保持较高的乳糖水解活性,筛选酶学特性适合在牛乳体系中高效水解乳糖的β-半乳糖苷酶生产菌株,是低乳糖牛乳加工产业关注的焦点。【目的】对天山中国一号冰川沉积物中分离的一株产低温β-半乳糖苷酶菌株的产酶条件和酶学特性进行研究。【方法】结合X-Gal平板法初筛和测定粗酶液酶活复筛,获得产低温β-半乳糖苷酶的菌株。通过形态学、生理生化试验及16S rRNA基因测序分析对筛选菌株进行鉴定,单因素摇瓶实验优化菌株的产酶条件,硫酸铵分级沉淀初步纯化β-半乳糖苷酶并对其酶学特性进行分析。【结果】通过形态学、生理生化特征和16S rRNA基因鉴定,确定菌株LW106为微杆菌属(Microbacterium)菌株;该菌株最适产酶温度为25°C,最佳产酶碳源为可溶性淀粉,培养基初始pH为7.0,接种量为3%;对初步纯化的低温β-半乳糖苷酶酶学性质的研究表明,LW106所产β-半乳糖苷酶的最适pH为6.0,最适反应温度为35°C,4°C时酶活为最大酶活的78%,4°C和pH 7.0时的稳定性最好,10 mmol/L的Na+对酶活性基本没有抑制作用,Ca~(2+)对酶活性具有一定的激活作用。【结论】菌株LW106所产低温β-半乳糖苷酶的酶学特性表明该酶在乳品低温加工领域具有进一步研究和应用的价值。  相似文献   

3.
采用人工底物邻硝基苯酚-β-D-半乳糖苷(o NPG)为筛选标记,从耐有机溶剂微生物菌库中,筛选出具有较高水解活性的β-半乳糖苷酶产生菌,再以乳糖为底物考察菌株低聚半乳糖的合成性能,筛选得到1株产β-半乳糖苷酶的Erwinia billingiae WX1。根据Gen Bank中相同属种的基因组序列推测β-半乳糖苷酶基因,克隆得到β-半乳糖苷酶基因gal,并在大肠杆菌中实现了来源于Erwinia billingiae菌β-半乳糖苷酶的克隆表达。该基因的开放阅读框(ORF)为1 428 bp,编码475个氨基酸,理论相对分子质量为5.2×104。镍柱法分离纯化得到电泳纯的β-半乳糖苷酶GAL,其酶学性质研究表明最适催化温度55℃,最适p H 7.0;Mg~(2+)、Mn~(2+)对该酶起较强促进作用,EDTA对该酶抑制作用较强。利用β-半乳糖苷酶GAL的转糖基作用,以乳糖为底物合成低聚半乳糖,初步优化的反应条件:底物乳糖质量浓度400 g/L,每克乳糖添加酶量1.0 U,在40℃反应16 h后,低聚半乳糖合成率达到34%(质量分数),显示了较好的开发前景。  相似文献   

4.
利用改良的MRS培养基,从鸡粪样本中分离到多株产β-半乳糖苷酶的乳酸菌菌株。酶学性质分析发现,菌株1-1产生的β-半乳糖苷酶在37℃~60℃相对稳定,37℃酶活力达到183.9NLU/g菌体干重。进一步分析16S rRNA基因序列,确定菌株1-1为阴道乳杆菌(Lactobacillus vaginalis)。扩增分析β-半乳糖苷酶编码基因lacL和lacM,结果发现LacL亚基有642个氨基酸,LacM亚基有321个氨基酸,与罗伊氏乳杆菌MM2-3相应蛋白的相似性分别为86%和84%。  相似文献   

5.
[目的]通过对天山1号冰川底部沉积层冻土中细菌的分离和产β-半乳糖苷酶低温菌株的筛选,了解天山冻土微生物的物种多样性,并对产β-半乳糖苷酶低温菌株的系统发育和生理多样性进行分析.[方法]以乳糖为主要碳源,X-Gal为显色剂,分离筛选出产低温β-半乳糖苷酶菌株.对细菌常规生理生化实验、最适生长温度、耐盐性、药物敏感性进行测定.根据16S rRNA基因序列初步确定产β-半乳糖苷酶低温菌种的系统进化地位,并采用BOX-PCR指纹图谱技术对16S rRNA基因高度同源性的菌株进一步区分.[结果]分离到90株可培养低温菌中25株可产β-半乳糖苷酶,其中76%为革兰氏阳性菌.依据生长温度,产酶菌株80%为嗜冷菌,20%为耐冷菌.在系统发育上,产酶菌株隶属于4个类群,其中肠球菌属(Enterococcus)占26%,短波单胞菌属(Brevundimonas)占22%,假单胞菌属(Pseudomonas)占13%.[结论]天山1号冰川底部沉积层冻土中产β-半乳糖苷酶的低温细菌具有比较丰富的物种和生理多样性.  相似文献   

6.
产β-葡聚糖酶基因工程菌发酵条件的优化   总被引:1,自引:0,他引:1  
目的以1株酶产量高、耐热性好的重组大肠埃希菌BL21为材料发酵生产β-葡聚糖酶。方法选用麸皮、豆粕等农副产品配制复合碳源、氮源,优化半合成发酵培养基,并通过正常试验确定最佳培养条件。结果研究得到摇瓶水平产β-葡聚糖酶的最佳培养基(g/L)为:麸皮6.7,玉米粉1.7,豆粕13.8,豆粉13.8,酵母粉7.0,NH4Cl 7.0,Na2HPO4.12H2O3.0,MgSO4.7H2O0.75,CaCl20.5,吐温80 0.8%。通过正交试验确定了产酶最佳初始pH为6.2,装样量为35 mL/250 mL,接种量为1%。采用优化后的工艺,在37℃200 r/min培养过夜,经乳糖诱导6 h后,最高酶活可达到830.7 U/mL,是初始产酶条件的3.4倍。结论该半合成培养基在重组大肠埃希菌产β-葡聚糖酶方面具有很大优势。  相似文献   

7.
以木聚糖酶、β-D-岩藻糖苷酶活力较高的海枣曲霉作为试验菌株。该菌株的粗酶液含有多种糖苷酶,活力较高的有木聚糖酶、地衣多糖酶、β-木糖苷酶、α-半乳糖苷酶、β-N-乙酰氨基葡萄糖苷酶、β-葡萄糖苷酶、β-D-岩藻糖苷酶及β-半乳糖苷酶等。其β-D-岩藻糖苷酶活力还高于β-半乳糖苷酶。将海枣曲霉培养不同时间后测活力,表明木聚糖酶在培养的第2天即大量产生,第3天达到高峰。Β-D-岩藻糖苷酶在第4天开  相似文献   

8.
碳源对K.fragilis LFS-8611β-D-半乳糖苷酶合成的影响   总被引:1,自引:0,他引:1  
探讨了碳源对脆壁克鲁维酵母(Kluyveromyces fragilis)LFS-8611生长、β-D-半乳糖苷酶合成的影响及碳源对该酶合成的诱导作用。脆壁克鲁维酵母(K,fragilis)LFS-8611生长与β-D-半乳糖苷酶合成同步。该菌株生长和产酶的最适碳源为半乳糖,乳糖次之。菌体生物量和酶活力随着培养基中乳糖浓度的增加而增加,乳糖浓度为12mg/mL,菌体生物量和酶活力达到峰值,分别为5.84g/L、19,12U/mL。半乳糖和乳糖对β-D-半乳糖苷酶合成具有诱导作用。诱导物浓度对β-D-半乳糖苷酶的诱导合成有较大影响。半乳糖诱导以山梨醇为碳源预培养的K.fragilis LFS-8611细胞合成β-D-半乳糖苷酶的最适浓度为10mg/mL。  相似文献   

9.
以Aspergillus nigerJ5为出发菌株,经Co60γ-射线诱变,筛选到一株β-葡聚糖酶和木聚糖酶活力都较出发菌株高的突变株A-25,其产β-葡聚糖酶和木聚糖酶的合适发酵条件为:大麦粉4%、玉米浆2.5%、NaNO30.4%、Na2HPO40.1%、MgSO4.7H2O0.03%、FeSO4.7H2O0.01%、CaCO30.5%、吐温-800.25%,初始pH6.7,300mL三角瓶的装液量为50mL,在此条件下培养84h,β-葡聚糖酶活力达到1203.9I U/mL,较出发菌株提高35.9%,木聚糖酶活力达到395.2I U/mL,较出发菌株提高27.8%。突变株粗酶液降解工业面粉非淀粉多糖的能力明显高于出发菌株。  相似文献   

10.
以前期里氏木霉RNA-seq中发现的7个糖苷水解酶基因为对象,分析其不同条件下的表达特性,以期为寻找新的纤维素降解功能酶提供证据。运用生物信息学方法,分析了7个基因可能的编码产物和结构特征。以不同的产纤维素酶菌株(QM 9414、RUT C30)为材料,采用实时荧光定量PCR,对7个糖苷水解酶基因(编号4–10)在各种碳源条件下转录情况与主要的3个纤维素酶基因cbh1,cbh2,egl1(编号1–3)进行了比较分析。信息学分析表明,7个基因编码蛋白分属于GH47(4号、5号),GH92(6–8号),GH16(9号),GH31(10号)糖苷水解酶家族,具有典型的信号肽序列。cbh1,cbh2,egl1基因在纤维素酶诱导条件下,转录水平均表现显著的增加,上调倍数以QM 9414菌株表现的最高。QM 9414菌株中,cbh1,cbh2,egl1基因在纤维素条件下的上调倍数显著高于乳糖,3个基因在RUT C30菌株中的转录水平则显示乳糖条件下上调幅度更大。7个糖苷水解酶基因也存在类似的情况,而且编码α-甘露糖苷酶和内切β-葡聚糖酶的8号、9号基因上调倍数在纤维素酶诱导条件下仅次于纤维素酶基因,而以甘油为碳源条件下,8号、9号基因上调倍数高于纤维素酶基因。4号基因在上述碳源条件下,转录水平变化不大。结果表明:4号基因可能是组成型表达。基因5、6、7、8、9、10的表达呈现明显的菌株和碳源依赖性,且在纤维素酶诱导条件下基本上是和3个纤维素酶基因共转录的。  相似文献   

11.
A xylanase gene (xyl11B) was cloned from Bispora sp. MEY-1 and expressed in Pichia pastoris. xyl11B, with a 66-bp intron, encodes a mature protein of 219 residues with highest identity (57.1%) to the Trichoderma reesei xylanase of glycoside hydrolase family 11. The purified recombinant XYL11B was acidophilic, exhibiting maximum activity at pH 2.6 and 65 °C. The enzyme was also thermostable, pH stable, and was highly resistant to both pepsin and trypsin, suggesting good performance in the digestive tract as a feed supplement to improve animal nutrition. The activity of XYL11B was enhanced by most metal ions but was inhibited weakly by Hg2+, Pb2+and Cu2+, which strongly inhibit many other xylanases. The specific activity of XYL11B for oat spelt xylan substrate was 2049 U mg?1. The main hydrolysis products of xylan were xylose and xylobiose.  相似文献   

12.
Endo-(1,4)-beta-xylanases of plant and fungal origin play an important role in the degradation of arabinoxylans. Two distinct classes of proteinaceous endoxylanase inhibitors, the Triticum aestivum xylanase inhibitor (TAXI) and the xylanase inhibitor protein (XIP), have been identified in cereals. Engineering of proteins in conjunction with enzyme kinetics, thermodynamic, real-time interaction, and X-ray crystallographic studies has provided knowledge on the mechanism of inhibition of XIP-I towards endoxylanases. XIP-I is a 30 kDa protein which belongs to glycoside hydrolase family 18, and folds as a typical (beta/alpha)8 barrel. Although the inhibitor shows highest homology with plant chitinases, XIP-I does not hydrolyse chitin; probably due to structural differences in the XIP-I binding cleft. The inhibitor is specific for fungal xylanases from glycoside hydrolases families 10 and 11, but does not inhibit bacterial enzymes. The inhibition is competitive and, depending on the xylanase, the Ki value can be as low as 3.4 nM. Site-directed mutagenesis of a xylanase from Aspergillus niger suggested that the XIP-I binding site was the conserved hairpin loop "thumb" region of family 11 xylanases. Furthermore, XIP-I shows the ability to inhibit barley alpha-amylases of glycoside hydrolase family 13, providing the first example of a protein able to inhibit members of different glycoside hydrolase families (10, 11, and 13), and additionally a novel function for a protein of glycoside hydrolase family 18.  相似文献   

13.
Triticum aestivum xylanase inhibitor I (TAXI-I) is a wheat protein that inhibits microbial xylanases belonging to glycoside hydrolase family 11. In the present study, recombinant TAXI-I (rTAXI-I) was successfully produced by the methylotrophic yeast Pichia pastoris at high expression levels (approximately 75 mg/L). The rTAXI-I protein was purified from the P. pastoris culture medium using cation exchange and gel filtration chromatographic steps. rTAXI-I has an iso-electric point of at least 9.3 and a mass spectrometry molecular mass of 42,013 Da indicative of one N-linked glycosylation. The recombinant protein fold was confirmed by circular dichroism spectroscopy. Xylanase inhibition by rTAXI-I was optimal at 20-30 degrees C and at pH 5.0. rTAXI-I still showed xylanase inhibition activity at 30 degrees C after a 40 min pre-incubation step at temperatures between 4 and 70 degrees C and after 2 h pre-incubation at room temperature at a pH ranging from 3.0 to 12.0, respectively. All tested glycoside hydrolase family 11 xylanases were inhibited by rTAXI-I whereas those belonging to family 10 were not. Specific inhibition activities against family 11 Aspergillus niger and Bacillus subtilis xylanases were 3570 and 2940IU/mg protein, respectively. The obtained biochemical characteristics of rTAXI-I produced by P. pastoris (no proteolytical cleft) were similar to those of natural TAXI-I (mixture of proteolytically processed and non-processed forms) and non-glycosylated rTAXI-I expressed in Escherichia coli. The present results show that xylanase inhibition activity of TAXI-I is only affected to a limited degree by its glycosylation or proteolytic processing.  相似文献   

14.
Xanthomonas axonopodis pv. punicae strain—a potent plant pathogen that causes blight disease in pomegranate—was screened for cellulolytic and xylanolytic enzyme production. This strain produced endo-β-1,4-glucanase, filter paper lyase activity (FPA), β-glucosidase and xylanase activities. Enzyme production was optimized with respect to major nutrient sources like carbon and nitrogen. Carboxy methyl cellulose (CMC) was a better inducer for FPA, CMCase and xylanase production, while starch was found to be best for cellobiase. Soybean meal/yeast extract at 0.5 % were better nitrogen sources for both cellulolytic and xylanolytic enzyme production while cellobiase and xylanase production was higher with peptone. Surfactants had no significant effect on levels of extracellular cellulases and xylanases. A temperature of 28 °C and pH 6–8 were optimum for production of enzyme activities. Growth under optimized conditions resulted in increases in different enzyme activities of around 1.72- to 5-fold. Physico-chemical characterization of enzymes showed that they were active over broad range of pH 4–8 with an optimum at 8. Cellulolytic enzymes showed a temperature optimum at around 55 °C while xylanase had highest activity at 45 °C. Heat treatment of enzyme extract at 75 °C for 1 h showed that xylanase activity was more stable than cellulolytic activities. Xanthomonas enzyme extracts were able to act on biologically pretreated paddy straw to release reducing sugars, and the amount of reducing sugars increased with incubation time. Thus, the enzymes produced by X. axonopodis pv. punicae are more versatile and resilient with respect to their activity at different pH and temperature. These enzymes can be overproduced and find application in different industries including food, pulp and paper and biorefineries for conversion of lignocellulosic biomass.  相似文献   

15.
With the progressive focus on renewable energy via biofuels production from lignocellulosic biomass, cellulases are the key enzymes that play a fundamental role in this regard. This study aims to unravel the characteristics of Thermotoga maritima MSB8 (Tma) (a hyperthermophile from hot springs) thermostable glycoside hydrolase enzyme. Here, a glycoside hydrolase gene of Thermotoga maritima (Tma) was heterologously expressed and characterized. The gene was placed in the pQE-30 expression vector under the T5 promotor, and the construct pQE-30-Gh was then successfully integrated into Escherichia coli BL21 (DH5α) genome by transformation. Sequence of the glycoside hydrolase contained an open reading frame of 2.124 kbp, encoded a polypeptide of 721 amino acid residues. The molecular weight of the recombinant protein estimated was 79 kDa. The glycoside hydrolase was purified by Ni+2-NTA affinity chromatography and its enzymatic activity was investigated. The recombinant enzyme is highly stable within an extreme pH range (2.0–7.0) and highly thermostable at 80 °C for 72 h indicating its viability in hyperthermic environment and acidic nature. Moreover, the Ca2+ and Mn2+ introduction stimulated the residual activity of recombinant enzyme. Conclusively, the thermostable glycoside hydrolase possesses potential to be exploited for industrial applications at hyperthermic environment.  相似文献   

16.
Fungi producing xylanases are plentiful but alkali-thermo-tolerant fungi producing cellulase-poor xylanase are rare. Out of 12 fungal strains isolated from various sources, Coprinellus disseminatus SW-1 NTCC 1165 yielded the highest xylanase activity (362.1 IU/ml) with minimal cellulase contamination (0.64 IU/ml). The solid state fermentation was more effective yielding 88.59% higher xylanase activity than that of submerged fermentation. An incubation period of 7 days at 37°C and pH 6.4 accelerated the xylanase production up to the maximum level. Among various inexpensive agro-residues used as carbon source, wheat bran induced the maximum xylanase titres (469.45 IU/ml) while soya bean meal was the best nitrogen source (478.5 IU/ml). A solid substrate to moisture content ratio of 1:3 was suitable for xylanase production while xylanase titre was repressed with the addition of glucose and lactose. The xylanase and laccase activities under optimized conditions were 499.60 and 25.5 IU/ml, respectively along with negligible cellulase contamination (0.86 IU/ml). Biochemical characterization revealed that optimal xylanase activity was observed at pH 6.4 and temperature 55°C and xylanase is active up to pH 9 (40.33 IU/ml) and temperature 85°C (48.81 IU/ml). SDS–PAGE and zymogram analysis indicated that molecular weight of alkali-thermo-tolerant xylanase produced by C. disseminatus SW-1 NTCC 1165 was 43 kDa.  相似文献   

17.
A complete gene, xyl10C, encoding a thermophilic endo-1,4-β-xylanase (XYL10C), was cloned from the acidophilic fungus Bispora sp. MEY-1 and expressed in Pichia pastoris. XYL10C shares highest nucleotide and amino acid sequence identities of 57.3 and 49.7%, respectively, with a putative xylanase from Aspergillus fumigatus Af293 of glycoside hydrolase family 10. A high expression level in P. pastoris (73,400 U ml−1) was achieved in a 3.7–l fermenter. The purified recombinant XYL10C was thermophilic, exhibiting maximum activity at 85°C, which is higher than that reported from any fungal xylanase. The enzyme was also highly thermostable, exhibiting ~100% of the initial activity after incubation at 80°C for 60 min and >87% of activity at 90°C for 10 min. The half lives of XYL10C at 80 and 85°C were approximately 45 and 3 h, respectively. It had two activity peaks at pH 3.0 and 4.5–5.0 (maximum), respectively, and was very acid stable, retaining more than 80% activity after incubation at pH 1.5−6.0 for 1 h. The enzyme was resistant to Co2+, Mn2+, Cr3+ and Ag+. The specific activity of XYL10C for oat spelt xylan was 18,831 U mg−1. It also had wide substrate specificity and produced simple products (65.1% xylose, 25.0% xylobiose and 9.9% xylan polymer) from oat spelt xylan.  相似文献   

18.
Renewable natural resources such as xylans are abundant in many agricultural wastes. Penicillium sp. AHT-1 is a strong producer of xylanolytic enzymes. The sequential activities of its xylanase, alpha-L-arabinofuranosidase, and beta-xylosidase on model hemicellulose oat-spelt xylan was investigated. Optimum production of the enzymes was found in culture containing oat-spelt xylan at 30 degrees C and initial pH 7.0 after 6 days. The enzymes were partially purified by ammonium sulphate fractionation and anion-exchange chromatography on DEAE-Toyopearl 650 S. The apparent molecular mass was 21 kDa, and the protein displayed an "endo" mode of action. The xylanase exhibited glycotansferase activity. It synthesized higher oligosaccharides from the initial substrates, and xylotriose was the shortest unit of substrate transglycosylated. Xylanolytic enzymes (enzyme mixture) produced by this Penicillium sp. interacted cooperatively and sequentially in the hydrolysis of oat-spelt xylan in the following order: alpha-L-arabinofuranosidase --> xylanase --> beta-xylosidase. All three enzymes exhibited optimal activity under the same conditions (temperature, pH, cultivation), indicating that they alone are sufficient to completely depolymerize the test xylan. Results indicate that the xylanolytic enzyme mixture of Penicillium sp. AHT-1 could be useful for bioconversion of xylan-rich plant wastes to value-added products.  相似文献   

19.
Bacteria modulate glycoside hydrolase expression in response to the changes in the composition of lignocellulosic biomass. The response of switchgrass-adapted thermophilic bacterial consortia to perturbation with a variety of biomass substrates was characterized to determine if bacterial consortia also responded to changes in biomass composition. Incubation of the switchgrass-adapted consortia with these alternative substrates produced shifts in glycoside hydrolase activities and bacterial community composition. Substantially increased endoglucanase activity was observed upon incubation with microcrystalline cellulose and trifluororacetic acid-pretreated switchgrass. In contrast, culturing the microbial consortia with ionic liquid-pretreated switchgrass increased xylanase activity dramatically. Microbial community analyses of these cultures indicated that the increased endoglucanase activity correlated with an increase in bacteria related to Rhodothermus marinus. Inclusion of simple organic substrates in the culture medium abrogated glycoside hydrolase activity and enriched for bacteria related to Thermus thermophilus. These results demonstrate that the composition of biomass substrates influences the glycoside hydrolase activities and community composition of biomass-deconstructing bacterial consortia.  相似文献   

20.
Direct utilization of untreated oil palm trunk (OPT) for cellulases and xylanase production by Aspergillus fumigatus SK1 was conducted under solid-state fermentation (SSF). The highest activities of extracellular cellulases and xylanases were produced at 80% moisture level, initial pH 5.0, 1 × 108 spore/g (inoculum) with 125 μm of OPT as sole carbon source. The cellulases and xylanase activities obtained were 54.27, 3.36, 4.54 and 418.70 U/g substrates for endoglucanase (CMCase), exoglucanase (FPase), β-glucosidase and xylanase respectively. The crude cellulases and xylanase required acidic condition to retain their optimum activities (pH 4.0). Crude cellulases and xylanase were more stable at 40 °C compared to their optimum activities conditions (60 °C for FPase and 70 °C for CMCase, β-glucosidase and xylanase). SDS-PAGE and zymogram analysis showed that Aspergillus fumigatus SK1 could secrete cellulases (endoglucanase, exoglucanase and β-glucosidase), xylanase and protease. Enzymatic degradation of alkaline treated OPT with concentrated crude cellulases and xylanases resulted in producing polyoses.  相似文献   

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