Characteristics of Aspergillus niger xylanases produced on rice husk and wheat bran in submerged culture and solid‐state fermentation for an applicability proposal

Xylanolytic rich filtrates were obtained by A. niger sp in both submerged and solid‐state culture using rice husk or wheat bran as the only carbon source. Filtrates obtained on rice husk showed the highest activities (~6500 and 5200 U g^?1, respectively). Independent of carbon source, these filtrates were very stable in an acidic pH range (4–7) and mild temperatures, with high half‐life time values (more than 7 h at 50 °C) in the corresponding inactivation kinetic models. Also the effect of different metallic ions and denaturing substances was verified finding that these enzymes are not metaloproteins, and metals as Hg²⁺ and Pb²⁺ caused the greatest loss of xylanolytic activity (not higher than 30%). Xylanases produced by this A. niger strain showed important features that make them potential candidates for applications on human and livestock food industries.     

Comparison of releasing bound phenolic acids from wheat bran by fermentation of three Aspergillus species

Wheat bran was fermented at 28 °C for 7 days under 70% humidity by Aspergillus niger, Aspergillus oryzae and Aspergillus awamori. Total phenolic content (TPC) of the unfermented sample was 1531.5 μg g^?1 wheat bran. After the fermentation of Aspergillus awamori, Aspergillus oryzae and Aspergillus niger, TPC reached 5362.1, 7462.6 and 10 707.5 μg g^?1, respectively. The antioxidant activity in the extractions of fermented wheat bran also increased significantly compared with the unfermented sample (P < 0.05). Aspergillus niger showed the greatest capacity to release bound ferulic acid (416.6 μg g^?1). Aspergillus oryzae and Aspergillus awamori had the advantages of releasing more chlorogenic acid (84.0 μg g^?1) and syringic acid (142.3 μg g^?1), respectively. The destructive effect of Aspergillus niger on wheat bran structure was the strongest, followed by that of Aspergillus oryzae. This effect of Aspergillus niger may be due to its higher cellulase, xylanase, arabinofuranosidase and β‐xylosidase activities. Besides, Aspergillus oryzae possessed higher β‐glucosidase activity, and Aspergillus awamori had higher α‐amylase and feruloyl esterase activities. Aspergillus niger may be the best to release bound phenolic acids in the three Aspergillus species. These will provide the helpful information for understanding mechanism of the fermentation by Aspergillus species releasing bound phenolic in wheat bran.     

Plackett-Burman设计在曲霉Aspergillus sp.GX-0010果糖基转移酶发酵条件主要因子筛选中的应用

试验采用Plackett-Burman试验设计,选取蔗糖、蛋白胨、硫酸亚铁、pH值、温度、培养时间、装液量,接种量共8个相关因素进行设计,统计分析表明,pH(p=0.019)、温度(p=0.003)、装液量(p=0.131)为对曲霉(Aspergillus sp.)菌株GX-0010产果糖基转移酶具有显著影响的因素。     

Characterization of an extracellular β‐d‐fructofuranosidase produced by Aspergillus niveus during solid‐state fermentation (SSF) of cassava husk

β‐d ‐Fructofuranosidases are biotechnologically important enzymes produced by various organisms. Here, Aspergillus niveus produced an extracellular β‐d ‐fructofuranosidase during SSF of cassava husk. This enzyme was purified 8.5‐fold (recovery of 5.2%). A 37‐kDa protein band was observed after 8% SDS‐PAGE. Native molecular mass is 91.2 kDa. Optimal temperature and pH of activity were 55°C and 4.5, respectively. The enzyme was stable at 50°C for 1 hr, and 80% of its activity was retained after 1 hr at pH 8.0. The enzymatic activity was improved by Mn²⁺, was resistant to most solvents, and was inhibited by Triton X‐100 and Tween 20. K_m and V_max with sucrose were 22.98 mM and 120.48 U/mg of protein, respectively. With Mn²⁺, these values were 16.31 mM and 0.30 U/mg of protein. The enzyme did not hydrolyze inulin and for this reason can be considered a true invertase. Thus, A. niveus β‐d ‐fructofuranosidase holds promise for invert sugar production.

Practical applications

β‐d ‐Fructofuranosidase is an enzyme that can be applied to different industrial sectors, especially food and beverage industries. It is responsible for the hydrolysis of sucrose and yields an equimolar mixture of D‐glucose and D‐fructose, named as inverted sugar syrup, with broad applications in the confectionery industry. The Aspergillus niveus enzyme hydrolyzed only sucrose here and can be considered a true invertase, showing its potential for application to invert sugar production. Besides, the use of cassava husk for enzyme production means an interesting utilization route of this agroindustrial residue. Thus, characterization of this enzyme is an important step for identification of its potential for practical applications.     

Preparation and characterisation of glyceollin‐enriched soya bean protein using solid‐state fermentation

Glyceollins, stress‐induced phytoalexins from parent soya bean isoflavones, were elicited with Aspergillus oryzae. This solid‐state fermentation facilitated the conversion of isoflavone glycosides into aglycones and glyceollins, which could mainly enrich in soya bean protein isolate (SPI) during protein preparation due to protein–polyphenol interactions. Glyceollin‐enriched SPI exhibited less flavour volatiles, higher solubility, lower whiteness and higher antioxidant activity than unfermented SPI. Fermented SPI was more easily to be digested during in vitro pepsin–trypsin digestion. This may be attributed to partial degradation of protein, especially α′ and α subunits of β‐conglycinin and acidic subunit of glycinin. The antioxidant activity of digestive products derived from fermented SPI was obviously enhanced with increasing digestion time due to simultaneous release of antioxidant peptides and glyceollins involved in the interior of protein molecule. These results suggest an effective technique for producing a nutrient‐enhanced SPI as novel functional ingredients applied in food industry.     

23株曲霉属菌种的形态学复核鉴定研究

对中国工业微生物菌种保藏管理中心(CICC)保藏的23株19种曲霉属菌种进行了形态学复核鉴定研究。根据《The Genus Aspergillus》、《中国真菌志——曲霉属及其相关有性型》和《Identification of commonAs-pergillusspecies》,采用曲霉属菌种形态观察的标准培养条件,以菌种培养特征和显微形态为依据进行复核鉴定。22株19种菌种的复核结果与原鉴定结果一致,其中5种5株菌种根据分类命名规则的最新进展重新命名;另1株CICC 2106,原定种为溜曲霉(Aspergillus tamarii),复核鉴定结果为黑曲霉(Aspergillus niger),ITS1-5.8S-ITS2序列分析和Biolog微生物快速分析实验支持复核结果。通过形态学复核鉴定,CICC保藏的23株曲霉属菌种原鉴定结果的准确性达到95.6%。     

米曲霉脂肪酶富集浓缩裂殖壶藻油脂中DHA的机理研究

本研究采用了米曲霉(Aspergillus oryzae, AO)脂肪酶水解法对裂殖壶藻油脂中的二十二碳六烯酸(Docosahexaenoic Acid, DHA)进行了浓缩。在AO脂肪酶最适反应条件下,水解12 h后,反应达到了平衡,产物中甘三酯含量降至40.2%,DHA含量升至55.43%,浓缩了1.58倍,回收率高达68.2%。通过气相色谱结合核磁共振碳谱(13C-NMR)对产物中甘油三酯脂肪酸组成及含量进行了分析,结果显示在酶解反应过程中,DHA倾向于留在甘三酯甘油骨架上,且sn-1,3位上的饱和脂肪酸易被水解而含量下降,表明AO脂肪酶水解反应对甘油骨架上的脂肪酸具有选择性,可将DHA富集在甘油三酯中。AO脂肪酶价格低廉,基于酶解反应的DHA富集工艺简单,深入了解反应的作用机制,将为后续的理论研究和实际应用提供依据。     

一株毛霉菌产脂肪酶特性及发酵条件研究

文中观察了一株产脂肪酶毛霉(Mucor sp.)菌株在橄榄油罗丹明B鉴定平板上的菌落形态,对其产脂肪酶进行了酶学特性研究,并探讨了该菌株产脂肪酶的发酵条件,优化了产酶发酵培养基和产酶发酵条件,得出了该菌产酶的最佳发酵条件为以1%全脂大豆粉为氮源,1%玉米浆为碳源,添加0.5%橄榄油和0.1% Tween-80,控制起始pH值为6.0.     

响应面法优化海洋弧菌产褐藻胶裂解酶发酵培养基

采用响应面法优化海洋弧菌X511的产酶发酵培养基,提高其胞内褐藻胶裂解酶产量。通过单因素试验研究了不同碳源、不同氮源、海藻酸钠、氯化钠、蛋白胨、硫酸亚铁、硫酸镁和磷酸氢二钾对菌株产胞内酶活力的影响,在此基础上,利用Plackett-burman试验确定海藻酸钠、氯化钠、蛋白胨和硫酸镁对胞内酶产量的影响。通过响应面试验构建回归方程,结果表明,最佳发酵培养基成分为海藻酸钠9.0 g/L,NaCl 31.6 g/L,蛋白胨15.0 g/L,MgSO4·7H2O 1.5 g/L。在此条件下,该菌株的胞内褐藻胶裂解酶的活力为（20.65±0.14） U/mL,较优化前的酶活提高了64.4%。     

Klebsiella sp.B-36的分离鉴定及产脂肪酶特性研究

从郑州西郊采集的土壤样品中筛选到一株产耐高温酸性脂肪酶菌株B-36,根据其形态、生理生化特征及16S rDNA序列分析初步鉴定为克雷伯氏茵(Klebsiella sp.).对该菌株产脂肪酶特性研究结果表明:该酶的适宜作用温度为60℃,适宜pH 4.0,该酶在60℃热处理70 min酶活力可保持在80％以上,说明该酶具有良好的热稳定性.同时,该酶在酸性环境中静置lh后还保持70％以上的酶活力,说明该酶在酸性条件下较稳定.金属离子Mg2+、Ca2、Na+以及EDTA对酶有明显的激活作用,Fe3+、Cu2+及ZN2+对酶有抑制作用,K+对酶几乎没有影响.     

Partial characterization of lipases produced by a newly isolated Penicillium sp. in solid state and submerged fermentation: A comparative study

The aim of this research was the partial characterization of enzymatic extracts produced by a newly isolated Penicillium sp. in submerged (SmF) and solid state fermentation (SSF). The partial characterization of the crude enzymatic extract obtained by SSF and SmF systems showed optimum activity at pH 5.5 and 47 °C, and pH 7.0 and 37 °C, respectively (15.17 U/mL and 11.28 U/mL). The crude enzymatic extracts obtained by SmF and SSF presented the best stability at pH from 4.9 to 8.5 and temperature from 25 °C to 35 °C and pH 7.0 and 25 °C, respectively. These results confirm the interesting potential of SSF, because, besides the higher activities obtained in this system, the half-life time at 25 °C was higher than that observed for the lipase extract obtained in the SmF system.     

黑曲霉B0201生料发酵产单宁酶的提取及酶学性质研究

对黑曲霉B0201利用五倍子为诱导物生料发酵产胞外单宁酶的提取及酶学性质进行了研究。结果表明:硫酸铵两步沉淀的饱和度为40%和90%;该酶的最适温度为40℃,最适pH为5·0,低于60℃时的热稳定性高,60℃以上迅速失活。Zn2+、Mg2+、吐温80、EDTA等对酶活力无明显影响,Fe3+、Cu2+、Fe2+、Ba2+、Mn2+、Ca2+、Al3+等对酶有抑制作用。以没食子酸丙酯（PG）为底物,单宁酶的米氏常数Km为0·514mmol/L,Vmax为71·8μmol/L·min。      

固态发酵豆粕的不同生产工艺及其营养品质比较

以米曲霉和植物乳杆菌WZ011为发酵菌种,研究了5种不同的固态发酵豆粕生产工艺及其营养品质。以灰分、粗蛋白量、可溶性蛋白量、游离总氨基酸量、氨基酸含量分布、酸溶性蛋白量、小肽含量、还原糖量、氮溶指数、蛋白分子量、脲酶含量、胰蛋白酶抑制因子含量以及体外消化率为指标,对发酵豆粕营养品质进行了比较和分析。结果表明,米曲霉单菌发酵后,高温水解处理对豆粕营养品质的提高有效,但在米曲霉和植物乳杆菌WZ011的双菌串联发酵过程中增加高温水解处理反而不利。在米曲霉有氧发酵后直接接种植物乳杆菌WZ011进行厌氧发酵条件下所得的豆粕营养品质最优,其中的胰蛋白酶抑制因子含量比原豆粕减少了91.8%,并含有小肽8.01%、乳酸4.95%、γ-氨基丁酸0.317 mg/g以及植物乳杆菌活菌数1.93×1010CFU/g。优化的豆粕发酵工艺操作简单且无污染,其产品富含营养。该工艺在饲料加工行业和养殖业具有应用意义。