与生产功能性低聚糖相关的酶(下)

介绍了与乳果糖、异麦芽低聚糖、低聚壳聚糖相关的酶及生产。乳果糖又称乳蔗糖，是在蔗糖分子的葡萄糖残基上接一个半乳糖残基构成的三糖，是在蔗糖、乳糖共存下，由节杆菌K-1乳糖苷酶的果糖基转移反应所生产的；异麦芽低聚糖是指含有异麦芽糖、异麦芽三糖、异麦芽四糖和泮糖等具有α～1，6键的分支低聚麦芽糖的混合物，异麦芽低聚糖是以淀粉为原料，经α-淀粉酶、β-淀粉酶或真菌α-淀粉酶的糖化作用生成麦芽糖后，在α-葡萄糖苷酶的转移反应下生成的；壳聚糖是甲壳动物和真菌细胞壁中的甲壳素（几丁质）经碱处理脱乙酰基而成的链状阳离子型多糖，壳寡糖是用壳聚糖酶水解而成的。     

高温α-淀粉酶产生菌的筛选及酶学性质研究

从酒厂高温曲中筛选到一株产高温α-淀粉酶的野生茼株，经初步鉴定为链霉菌，命名为Streptomycessp．1109。在45℃条件下，该茵株固体发酵产酶活力达到169．13u／g。通过酶学性质研究，该酶反应最适温度为85℃，最适pH为6．5，具有较高的热稳定性。     

青霉菌α-葡萄糖苷酶固体发酵及酶学特性的研究

研究青霉菌种P1固体培养生产α-葡萄糖苷酶的发酵条件,固体培养条件下培养基中碳源、氮源及添加物对青霉P1产α-葡萄糖苷酶的影响以及青霉P1产α-葡萄糖苷酶的最适温度、pH、热稳定性及pH稳定性等酶学特性。     

产β-葡萄糖苷酶野生真菌的筛选鉴定及酶学性质研究

从原始森林腐木的土壤中筛选得到1株高产β-葡萄糖苷酶活力菌株Lcxs9,表型分析及ITS rDNA序列分子鉴定为芽枝霉菌,酶活为7.18U/mL,在pH值为4~9范围内,60℃以下酶活力稳定,酶谱分析芽枝霉菌Lcxs9可以产2种β-葡萄糖苷酶。该文首次报道芽枝霉菌产高活性β-葡萄糖苷酶。     

芡实淀粉的酶解特性及体外消化模拟分析

研究芡实淀粉的酶解特性及其在模拟过程中的消化特性。采用α-淀粉酶水解法,以酶解液中还原糖释放率为指标,对芡实淀粉的酶解特性进行分析。结果表明,α-淀粉酶的最优酶解条件为:α-淀粉酶用量350U/g、底物质量浓度为10g/100mL、pH值为6,于50℃水浴中水解60～80min。在此条件下,芡实淀粉酶解液中还原糖释放率可达79.61%。体外消化模拟结果显示,芡实淀粉在模拟消化中的还原糖和可溶性糖释放率均远低于酶解过程;且与米淀粉相比,芡实淀粉较难消化。研究认为,芡实淀粉在α-淀粉酶作用下,较易水解;消化模拟过程中,芡实淀粉的可消化性稍低于米淀粉,可能与其中残留的植物多酚类物质有关。     

根霉PE-8菌株淀粉降解酶类的研究菌株的选育及其酶解淀粉产物的鉴定(I)

从淀粉厂土样等样品中分离筛选到一支产淀粉降解酶的根霉菌株P78,经紫外线及Co60辐射诱变和自然分离,获得一支突变菌株PE-8,在麸曲培养基上,46～48℃、固态培养22～24h,酶活力达3000U/g（干）。经高压液相色谱和纸层析分析证明,其分泌的淀粉降解酶类作用于适当液化的玉米淀粉产物中麦芽三糖至麦芽八糖的比例达77.6％、葡萄糖含量仅为3.03％,属于麦芽低聚糖,说明根霉PE-8菌株分泌的淀粉降解酶类不同于葡萄糖淀粉酶或α-淀粉酶,属于低聚糖酶。     

产右旋糖酐酶菌株的筛选、鉴定及酶学性质研究

该研究从连云港海域海泥中筛选产右旋糖酐酶菌株,对其进行形态学观察、生理生化试验及分子生物学鉴定,并对其产右旋糖酐酶的酶学性质、酶解产物组分及抗氧化活性进行研究。结果表明,筛选得到一株产右旋糖酐酶菌株GN02,其被鉴定为芽孢杆菌（Bacillus sp.）。菌株GN02产右旋糖酐酶的最适温度和pH分别为20 ℃和7.0,在25～40 ℃、pH 5.0～9.0范围具有良好的稳定性。酶解1 h的主要产物为异麦芽四糖（85.6%）和异麦芽三糖（14.3%）。酶解产物清除羟基自由基、1,1-二苯基-2-三硝基苯肼（DPPH）和超氧阴离子自由基的半抑制浓度（IC50值）分别为0.42 mg/mL、2.98 mg/mL和11.54 mg/mL。     

β-葡聚糖酶高产菌株的分离筛选及其新菌种初步鉴定

根据刚果红与β-1，3-1，4-葡聚糖紧密结合而保持红色的特征，采用改进的方法筛选β-葡聚糖酶高产霉菌。从牛的瘤胃中筛选出产酶活力高的17株霉菌中获得一株高产β-葡聚糖酶的曲霉，在摇瓶条件下产酶活力达2269u／ml。经初步鉴定，该菌株为局限曲霉。     

酶解法提高南瓜浆中可溶性糖的研究

采用热烫打浆法制取的南瓜原浆中可溶性糖含量为5.4%,本研究利用果胶酶、α-淀粉酶和糖化酶通过控制酶水解过程,提高了南瓜浆中可溶性糖的含量。水解工艺研究的结果表明：果胶酶量和酶解温度对可溶性糖含量有显著影响,在最佳酶解工艺条件下制得的南瓜浆可溶性糖含量为9.4%。     

嗜糖假单胞菌麦芽四糖淀粉酶的枯草芽孢杆菌表达及酶学性质分析

麦芽四糖淀粉酶是淀粉酶中第3种外切型酶,可以顺序地从淀粉非还原性末端依次切割第4个α-1,4糖苷键,产物为麦芽四糖,广泛应用于食品、医疗保健等领域。该研究采用含有P43启动子和SacB信号肽的pWB980枯草芽孢杆菌表达载体,连接嗜糖假单胞菌来源的麦芽四糖淀粉酶基因,获得了重组菌pWB980-G4/1A747,实现了麦芽四糖淀粉酶在枯草芽孢杆菌中的外分泌表达,并具有生物学活性。对表达产物进行酶学性质分析,结果表明麦芽四糖淀粉酶可广泛作用于7种不同来源的淀粉,生成单一产物麦芽四糖。最适反应温度为50℃,最适pH为7.0。进一步对pWB980-G4/1A747菌株进行发酵条件优化,得到其最佳活化时间为5 h,接种量为5%(v/v),通气量为20 mL/150 mL,培养时间为24 h,培养温度为37℃。     

柠檬苦素降解菌的分离筛选与分类鉴定

以新鲜醋醅为分离源,分离得到5株具有柠檬苦素降解活性的菌种,对柠檬苦素的最大降解率可达(58.86±2.81)%,发酵液的酶活力为(120.09±1.32)U/mL。基于形态特征、生理生化特性和16S rDNA序列分析结果,所得5 株菌均属芽孢杆菌属(Bacillus),其中2株为Bacillus siamensis,1株为解淀粉芽孢杆菌(Bacillus amyloliquefaciens),1株为短小芽孢杆菌(Bacillus pumilus),降解能力最强的1株为芽孢杆菌种Bacillus tequilensis。     

促酱醪发酵芽孢杆菌的筛选及应用

用酪素平板法从高盐稀态酱醪中筛选出56 株蛋白酶活性较好的菌株,牛津杯法复筛后制曲测定酶活性,得到淀粉酶活性最高的菌株CS1.11、蛋白酶活性最高的菌株CS1.13及纤维素酶活性最高的菌株CS1.17;16S rRNA序列测定结合形态学分析,CS1.11、CS1.13、CS1.17分别鉴定为贝莱斯芽孢杆菌（Bacillus velezensis）、甲基营养型芽孢杆菌（B. methylotrophicus）、枯草芽孢杆菌（B. subtilis）;分别将3 株实验菌与对照菌枯草芽孢杆菌CS1.03单独进行制曲后盐卤发酵,发现CS1.13发酵酱油氨态氮质量浓度最高,为5.12 g/L,CS1.11发酵酱油还原糖质量浓度最高,为27.20 g/L,与其酶活性结果一致,4 株菌对酱油总酸含量影响不大;顶空固相微萃取气相色谱-质谱联用内标法定性及定量分析发酵酱油发现,3 株实验菌与对照菌均具有产生吡嗪类物质及其前体乙偶姻和2,3-丁二醇的优势,且3 株实验菌优于对照菌;吡嗪类物质能赋予酱油良好的风味及健康因子,是芽孢杆菌酱油发酵的特征风味物质。筛选自高盐稀态酱醪的芽孢杆菌CS1.11、CS1.13、CS1.17有促酱醪发酵、丰富酱油风味、增进健康因子的潜力,具备良好的应用前景。     

米曲霉优良菌株的筛选及在制曲发酵西瓜黄豆酱中的应用

为获得蛋白酶、淀粉酶活性优良的米曲霉菌株,采用牛津杯双层平板法初筛、制曲分析酶活性复筛的方法,从制酱用成品曲中获得1?株淀粉酶活性优良菌株CS3.04和1?株蛋白酶活性优良菌株CS3.22,结合形态特征,ITS?rRNA序列分析鉴定为米曲霉。将2?株米曲霉分别进行单一菌种制曲及混合菌种制曲发酵西瓜黄豆酱,与商业米曲霉菌株制曲发酵进行对比,结果显示：不同制曲方式发酵西瓜黄豆酱的理化指标变化趋势保持一致,混合菌种制曲发酵样品的还原糖及氨态氮含量最高,分别为107.37、6.76?g/kg,比接种商业米曲霉菌株制曲发酵的样品分别提高了11.02%、5.56%;采用液液萃取-气相色谱-质谱联用技术定性及定量分析西瓜黄豆酱的挥发性风味物质,发现混合菌种制曲发酵具有产醛类、醇类、酮类及短链酯类物质的优势,而接种CS3.04单一菌种制曲发酵更有利于产酸类及酚类物质;混合菌种制曲发酵样品整体感官评分优于单一菌种制曲发酵,且在香气与滋味上占有优势。混合菌种制曲发酵工艺因CS3.04和CS3.22的酶系互补作用,有效地提升了西瓜黄豆酱的品质。     

Inhibition of Listeria monocytogenes in cold-smoked salmon by Carnobacterium piscicola CS526 isolated from frozen surimi

Strain CS526 was isolated from frozen surimi and identified as a bacteriocin producer that had strong inhibitory activity against Listeria monocytogenes. Strain CS526 was identified as Carnobacterium piscicola by partial 16S rDNA sequence similarity. The ability of this bacteriocinogenic strain and nonbacteriocinogenic C. piscicola JCM5348 to inhibit the growth of L. monocytogenes was examined in culture broth incubated at 12 degrees C and cold-smoked salmon stored at 4, 12, and 20 degrees C. L. monocytogenes viable counts in the culture broth rapidly declined from 10(6) colony-forming units per ml to less than 10 colony-forming units per ml within 1 day at 12 degrees C in the presence of C. piscicola CS526. At 4 and 12 degrees C, inhibition of L. monocytogenes on salmon depended on the initial inoculum level of C. piscicola CS526. However, C. piscicola CS526 was bactericidal to L. monocytogenes within 21 and 12 days at 4 and 12 degrees C in cold-smoked salmon, respectively, even when the initial inoculum levels were low. C. piscicola CS526 suppressed the maximum cell number of L. monocytogenes by two and three log cycles, even at 20 degrees C. However, C. piscicola JCM5348 did not prevent the growth of the pathogen, except at 4 degrees C. Bacteriocin was detected in the samples coinoculated with C. piscicola CS526. The study shows that C. piscicola CS526 might have potential for biopreservation of refrigerated foods against L. monocytogenes.     

Microbial composition of Korean kefir and antimicrobial activity of Acetobacter fabarum DH1801

Kefir is a probiotic dairy product containing multiple species of lactic acid bacteria, acetic acid bacteria, and yeast, with varying microbial composition depending on geographical origin. In the present study, we characterized the acetic acid bacterial population in Korean kefir by next-generation sequencing-based community analysis and isolated a novel acetic acid bacterial strain, Acetobacter fabarum DH1801. To evaluate its potential application in the food industry, the antimicrobial activity of A. fabarum DH1801 against seven foodborne pathogens (Bacillus cereus, Staphylococcus aureus, Listeria monocytogenes, Cronobacter sakazakii, Salmonella Enteritidis, enterotoxigenic Escherichia coli, and Shigella flexneri) was analyzed by growth curve analysis. Remarkably, the culture filtrate of the novel isolate inhibited the growth of all seven pathogenic bacteria in a dose-dependent manner, which was superior to acetic acid solution of same pH value. Our findings suggest that the A. fabarum DH1801 strain forms a protective barrier during kefir fermentation against contamination by foodborne pathogens.     

Classification of a bacterial isolate, from pozol, exhibiting antimicrobial activity against several gram-positive and gram-negative bacteria, yeasts, and molds

A bacterial isolate, designated CS93, capable of producing a broad-spectrum antimicrobial compound(s) effective against gram-positive and gram-negative bacteria, yeasts, and molds was isolated from pozol, a fermented maize product. This strain was phenotypically similar to another pozol isolate that was previously designated as Agrobacterium azotophilium by other investigators. By using biochemical, phenotypic, and 16S rRNA sequence analysis, both pozol isolates were identified as members of the genus Bacillus, possibly a variant of Bacillus subtilis. While the antimicrobial compound(s) was initially produced only on a solid medium, parameters were identified for production in broth. The compound(s) was heat stable (121 degrees C for 15 min), exhibited activity over a wide pH range (pH 3 to pH 11), and was inactivated by pronase E. The antimicrobial compound(s) was bactericidal and bacteriolytic against Escherichia coli V517, bacteriostatic against Micrococcus luteus, and fungistatic against Saccharomyces cerevisiae. The inhibitory compound(s) could possibly serve as a food biopreservative.     

Physiological behavior and quality traits during fruit growth and ripening of four Amazonic hot pepper accessions

BACKGROUND: Skin color, acid content and changes in other chemical components have been developed as indicators of maturation in fruits of the Capsicum type. RESULTS: Fruit growth and ripening in four hot pepper accessions (CS) from C. frutescens (CS376) and from C. annuum (CS219, CS049 and CS032) were monitored in three commercial Colombian Amazonic orchards. The time between fruit setting and commercial pepper fruit maturity was 41 ± 5 days for CS219, while CS032, CS049 and CS376 required 47 ± 3 days. Three stages of development were identified. The first stage was cell division in the accessions and a transient peak in respiration rate in CS049. A second stage of fruit growth occurred due to maximum cell expansion and some transient peaks of respiration rate also took place. Finally, a plateau occurred as fruit reached full maturity and followed typical non‐climacteric behavior. CS032 and CS219 were pungent with increasing levels of alkaloids (capsaicin and dihydrocapsaicin) during fruit growth, although CS376 with its constant and higher levels of the former capsaicinoids early in fruit growth was not pungent, and neither was CS049. Morphological traits and fresh and dry weight together with color coordinates could be used to discriminate among accessions as revealed by two axes of the canonical discriminant analysis (99.9% total variance explained). CONCLUSIONS: In general, the time from fruit set and the apex skin color changes and accompanying morphological traits, were reasonable indicators of maturity in Amazonian hot pepper fruits. Multivariate analysis was able to discriminate among accessions. Copyright © 2008 Society of Chemical Industry     

Effect of heating temperature,pH, concentration and starch/whey protein ratio on the viscoelastic properties of corn starch/whey protein mixed gels

The viscoelastic properties of corn starch (CS) gels were more dependent on heating temperature, while the properties of whey protein isolate (WPI) gels were more dependent on pH. Thus heating temperature (75, 85, 95 °C) and pH (5, 7, 9) were varied to obtain a series of mixed gels with interesting viscoelastic properties. WPI gels showed extensive stress relaxation (SR) indicative of a highly transient network structure, while CS gels relaxed very little in 2000 s. Based on SR results, it appeared that CS/WPI mixed gels with 25 and 50% CS formed compatible network structures at 15% total solids only at pH 9. This supposition was supported by SEM microstructures obtained for dehydrated gels and a synergistic increase in the large‐strain fracture stress for these gels. Some synergy was also found for mixed gels at 30% total solids at pH 9, while at pH 7 the mixed gels seemed to contain separate additive WPI and CS networks unlike the case for pH 7 at 15% total solids. In both cases (15 and 30% total solids) the degree of elasticity of the mixed gels decreased as the WPI content increased. Mixed gels (CS:WPI = 0.5) at pH 9 showed increased fracture stress and fracture strain relative to the same gels at pH 7. This suggests that a unique chemical compatibility exists at pH 9 and results in gels that combine the elasticity of CS and the internal stress dissipation of WPI. © 2001 Society of Chemical Industry     

响应面法优化鹅全骨硫酸软骨素的酶法提取工艺

采用麻阳鹅鹅全骨为原料,以硫酸软骨素（chondroitin sulfate,CS）的提取率为指标,对运用碱提、复合酶解、醇沉法提取CS的工艺进行研究,确定使用胃蛋白酶进行酶解后,通过单因素试验和响应面优化试验,应用Box-Behnken实验设计建立二次多项式数学模型,进行响应面分析,确定胃蛋白酶酶解提取CS的最佳工艺参数。结果表明：碱提、复合酶解、醇沉法胃蛋白酶酶解提取鹅全骨CS的最佳工艺为加酶量1.55 g/L、酶解时间6.4 h、酶解温度42 ℃、pH值3.09,在此条件下CS的提取率为12.13%;通过高效液相色谱测定可知,提取物为CS和盐酸氨基葡萄糖。     

白酒黄水中纤维素降解菌的分离鉴定及产酶活性研究

为拓展纤维素降解菌资源,以羧甲基纤维素钠（CMC-Na）为唯一碳源作初筛培养基,从浓香型白酒发酵副产物黄水中分离得到18株具有产纤维素酶能力的菌株进行纯培养。形态学、生理生化和系统发育鉴定结果显示,菌株XH01、XH04、XH05、XH18为Bacillus cereus,菌株XH34为Bacillus circulans,菌株SW01、SW05为Bacillus megaterium,菌株SW02为Bacillus endophyticus,菌株SW03、SW04为Bacillus simplex,菌株SW09、SW13为Bacillus bataviensis。菌株ZL08为Penicillium camemberti,菌株ZL13为Aspergillus fumigatus,菌株ZL04和ZL25为Penicillium chrysogenum,菌株ZL15和ZL17为Alternaria tenuissima。利用二硝基水杨酸法对菌株发酵液纤维素酶活进行研究,结果表明,菌株SW02的产酶活性较高,其羧甲基纤维素酶活为153.36 U/mL,β-葡萄糖苷酶活为126.00 U/mL,微晶纤维素酶活为17.64 U/mL,滤纸酶活为30.48 U/mL。