肉桂醛、柠檬醛抗黄曲霉作用的研究

目的:研究肉桂醛、柠檬醛的抗黄曲霉作用。方法:在含不同浓度药物的蔡氏培养液中接种一定量的黄曲霉孢子,每隔 4h分别取定量培养液涂布于蔡氏培养皿上进行霉菌计数,直到48h。 26.5℃培养 72h后计数萌发的霉菌孢子;用扫描电镜观察药物作用后黄曲霉的形态、表面结构的变化。结果:与对照组比较,肉桂醛、柠檬醛的浓度分别在≥0.05μg/ml、0.28μg/ml作用4h后,萌发的黄曲霉孢子数明显减少;肉桂醛、柠檬醛作用后黄曲霉孢子菌丝的形态、表面结构明显改变。结论:肉桂醛、柠檬醛对黄曲霉孢子萌发有显著的抑制作用,柠檬醛抑制黄曲霉孢子的萌发更迅速,两者可能通过破坏真菌细胞结构起抗菌作用。     

农用废弃物固态发酵生产衣康酸工艺研究

以土曲霉AS32811为发酵菌种,农用废弃物麸皮7.5g,玉米芯6.0g为出发培养基,在自然pH值条件下采用单因素试验研究碳源、氮源、无机盐对衣康酸产酸效果的影响。结果显示,该菌可以利用实验所选择的碳源生产衣康酸,葡萄糖为碳源时得率最高;氮源实验结果表明,NH4NO3是最适的产酸氮源。在单因素试验的基础上进行了五因素四水平的正交试验以优化产酸工艺。衣康酸生产的优化条件为:250mL三角瓶中加入玉米芯7.5g、麸皮6.0g、葡萄糖4g、营养液25mL(NH4NO3,4g/L;KH2PO4,0.1g/L;MgSO4,6g/L;C6H12O6,4g;ZnSO4.7H2O,0.015g/L),接种量为1mL(1×107孢子/mL)、温度36℃、湿度为65%条件下自然发酵72h,衣康酸产率可达63.5%。以土曲霉AS32811为发酵菌种,农用废弃物麸皮7.5g,玉米芯6.0g为出发培养基,在自然pH值条件下采用单因素试验研究碳源、氮源、无机盐对衣康酸产酸效果的影响。结果显示,该菌可以利用实验所选择的碳源生产衣康酸,葡萄糖为碳源时得率最高;氮源实验结果表明,NH4NO3是最适的产酸氮源。在单因素试验的基础上进行了五因素四水平的正交试验以优化产酸工艺。衣康酸生产的优化条件为:250mL三角瓶中加入玉米芯7.5g、麸皮6.0g、葡萄糖4g、营养液25mL(NH4NO3,4g/L;KH2PO4,0.1g/L;MgSO4,6g/L;C6H12O6,4g;ZnSO4.7H2O,0.015g/L),接种量为1mL(1×107孢子/mL)、温度36℃、湿度为65%条件下自然发酵72h,衣康酸产率可达63.5%。     

Ellagic Acid Production from Biodegradation of Creosote Bush Ellagitannins by Aspergillus niger in Solid State Culture

The ability of Aspergillus niger GH1 in converting creosote bush ellagitannins into ellagic acid (EA) was evaluated in solid state culture. Creosote bush leaves were used to extract the ellagitannins fraction, which was impregnated in polyurethane foam used as support of solid state culture. Ellagitannins content, EA accumulation, and the related enzymatic activities were evaluated. A. niger GH1 was able to completely degrade creosote bush ellagitannins with an EA yield of 23.1% at 36 h of culture. The ability to degrade creosote bush ellagitannins exhibited by A. niger GH1 was clearly associated to an ellagitannin-hydrolysing enzyme with a maximum activity of 43 U/l, while that ability was not associated to tannase activity that was detected in the culture extract. This study demonstrated the great ability of A. niger GH1 to hydrolyze ellagitannins and the potential of solid state culture to produce the antioxidant EA by degradation of creosote bush ellagitannins.     

Effect of Soybean Volatile Compounds on Aspergillus flavus Growth and Aflatoxin Production

ABSTRACT:  Soybean homogenates produced volatile compounds upon exposure to lipase. These induced volatiles were identified by SPME. Seventeen volatile compounds identified by SPME were chosen for determination of their ability to inhibit Aspergillus flavus growth and aflatoxin B₁ (AFB1) production in a solid media assay. These volatiles included aldehydes, alcohols, ketones, and furans. Of the tested compounds, the aldehydes showed the greatest inhibition of fungal growth and AFB1 production. These compounds inhibited up to 100% of the observed growth and AFB1 production as compared to the controls. The greatest activity by the aldehydes to disrupt growth was ranked as follows: 2,4 hexadienal > benzaldehyde > 2-octenal > ( E )-2-heptenal > octanal > ( E )-2-hexenal > nonanal > hexanal. The greatest activity by the aldehydes to reduce AFB1 was ranked as follows: ( E )-2-hexenal > 2,4 hexadienal > ( E )-2-heptenal > hexanal > nonanal. ( E )-2-hexenal and ( E )-2-heptenal were tested further in an A. flavus -inoculated corn kernel assay. Both compounds prevented colonization by A. flavus and eliminated AFB1 production when exposed to compound volumes < 10 μL as also shown in the solid media assay. The results suggest that soybeans react to lipase by production of potent antifungal volatiles.     

枯草芽孢杆菌和黑曲霉固态发酵制备核桃多肽的工艺条件优化

本研究以核桃粕为原料,对比探究了枯草芽孢杆菌(Bacillus subtilis 10160)、黑曲霉(GIM3.452)两株菌固态发酵制备核桃粕多肽的发酵生产性能,优化了两株菌发酵条件,筛选得到了最优的发酵条件参数。首先对影响固态发酵过程中多肽产量的主要因素(发酵时间、原料粒径、发酵温度、接种量和料液比)进行了研究,并以多肽产量为评价指标进行单因素逐步优化,研究结果表明,枯草芽孢杆菌(Bacillus subtilis 10160)固态发酵条件为:发酵时间3 d,原料粒径40目,料液比1:1.25,接种量5%,发酵温度28℃,此条件发酵后核桃粕多肽含量可达243.97 mg/g;黑曲霉固态发酵条件为:发酵时间4 d,原料粒径40目,发酵温度28℃,接种量15%,料液比1:1.25,此条件发酵后核桃粕多肽含量可达158.61 mg/g。通过分子量分布测定,进一步验证了枯草芽孢杆菌固态发酵制备核桃粕多肽产量高于黑曲霉。     

牛磺酸对米曲霉蛋白酶活性影响的初步研究

将牛磺酸作为米曲霉生长的强化剂,对米曲霉生长阶段的发芽率、孢子量、蛋白酶活进行了研究。结果表明,添加一定浓度的牛磺酸对米曲霉的生长有促进作用,牛磺酸的添加量0.1%、温度30℃平板培养5 h,米曲霉发芽率为95.12%,比空白组提高了10.3%;牛磺酸添加量0.1%、温度30℃发酵培养基培养72 h,米曲霉孢子数为1.09×1010个/g,比空白组提高了60.3%,米曲霉中性蛋白酶活达到15548 U/g,比空白组提高了38.8%。添加牛磺酸提高了米曲霉的产酶能力,为牛磺酸作为功能因子添加于豆制品提供了理论依据。      

高活力酸性蛋白酶酱油菌种的选育

本文通过对生产上使用的3.042米曲霉进行筛选，得到了酸性蛋白酶活力较高的菌株。将其与原始菌株混合制曲和发酵，可有效提高全氮利用率和氨基酸生成率。     

二氢杨梅素抑制黄曲霉菌生长的机制

本研究探讨了二氢杨梅素对黄曲霉的抗真菌活性和潜在的抗真菌机制。首先,通过抑菌实验证明,二氢杨梅素对黄曲霉孢子和菌丝的最小抑菌质量浓度（minimum inhibitory concentration,MIC）均为4 mg/mL。通过荧光增白剂（calcofluor white,CW）和碘化丙锭（propidium iodide,PI）染色实验证明,二氢杨梅素处理后黄曲霉细胞壁和细胞膜受损。与对照组相比,1/2 MIC和MIC组黄曲霉细胞内容物释放量（OD260 nm）分别增加了3.14 倍和5.93 倍,细胞外相对电导率和pH值均升高,MIC的二氢杨梅素对黄曲霉的呼吸抑制率达25.82%。这些结果表明,二氢杨梅素通过破坏细胞壁和细胞膜的完整性以及干扰呼吸代谢发挥抗菌活性。此外,二氢杨梅素在MIC时能够完全抑制黄曲霉在花生和玉米籽粒上的萌发,因此,二氢杨梅素可作为一种有效的抗真菌天然化合物应用于粮食及农产品储藏中。     

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。     

Chitosan Polymer as Bioactive Coating and Film against Aspergillus niger Contamination

ABSTRACT: The inhibitory activity of chitosan-based edible coatings and films was assessed against the Aspergillus niger food pathogen and deterioration microorganism. Spore-counting assays showed an almost total inhibition of A. niger growth when either film-forming solution or film were used at a low concentration of chitosan (0.1% w/v). Epifluorescence microscopic results showed the action of chitosan on the relative proportion of RNA compared with DNA. The water vapor permeability (WVP) of chitosan film was relatively low compared with the poor moisture barrier of some polysaccharide films. Moreover, a coating with chitosan film on an agar gel, used as a food model, induced a 30% reduction in water loss. These results showed potential applications of chitosan-based films as bioactive packaging with properties to limit the food dehydration phenomenon.