微生物发酵法制备太平洋牡蛎水解液

将米曲霉Aspergillus oryzae AS3.951接种到太平洋牡蛎(Ostreagigas thunberg)肉匀浆液中发酵培养,利用米曲霉产生的蛋白酶和淀粉酶水解牡蛎肉制备牡蛎水解液。通过单因素试验及正交试验探索发酵条件对太平洋牡蛎蛋白质回收率和糖原回收率的影响,发现起始pH为7.0时,蛋白质浓度为15%,装液量20%(V/V),140 r/min,30℃发酵48h,蛋白质回收率和糖原回收率最大,分别为85.33%和90.52%。这表明利用米曲霉发酵太平洋牡蛎制备水解液是可行的,并为进一步利用统计学方法提高米曲霉发酵太平洋牡蛎制备高蛋白回收率和糖原回收率水解液奠定基础。     

耐盐米曲霉CICIM F0899在酱油酿造过程中的应用

耐高盐环境的蛋白酶对酱油工业有着积极作用。该实验对1株产耐盐蛋白酶的米曲霉CICIM F0899在高盐稀态酱油发酵过程中的作用进行了研究,并同沪酿3042进行了比较。结果表明,在酱醪发酵阶段,微生物代谢产酸使酱醪pH持续下降,影响了蛋白酶的活性,导致酱油中氨基态氮和风味物质含量的变化,在180天时氨基态氮含量达到0.62 g/100 mL,比沪酿3042高11.11%。利用气相色谱-质谱联用(GC-MS)对挥发性成分进行了分析鉴定,检测出酱醪中7大类共49种挥发性化合物,其中酯类、杂环类化合物的含量明显高于沪酿3042,而醛类物质的含量相对较少。因此,米曲霉CICIM F0899在氨基态氮含量和风味组成方面都具有更加明显的优势。     

米根霉F1-ATPase活性降低突变株的筛选研究

本实验采用同步辐射软X射线Nk诱变米根霉,获得一株新霉素抗性突变株NA-2,该菌株F1-ATPase活性降低86.82%,胞内ATP含量下降18.99%,最终菌体浓度为出发菌株的79.22%,发酵周期缩短了12h,葡萄糖平均消耗速度和L-乳酸生产强度分别高出25.17%和32.57%,平均葡萄糖消耗比速(qs)、L-乳酸生成比速(qp)和细胞比生长速率(μ)分别提高86.42%、128.13%和60.0%,但胞内能荷变化不明显。进一步研究发现,突变株糖酵解途径中关键酶磷酸果糖激酶(PEK)、丙酮酸激酶(PK)和磷酸甘油醛激酶(GAPDH)的活性较原始菌株提高了58.34%、23.53%和11.29%,乙醇脱氢酶(ADH)活性降低了32.11%,乳酸脱氢酶(LDH)活性提高了42.27%。结果表明,降低米根霉F1-ATPase活性有效地提高了糖酵解关键酶活性而加速葡萄糖代谢,提高了L-乳酸生产强度。     

Relationship Between Extracellular Cellulase,Pectinase and Xylanase Activity of Isolated Aspergillus oryzae Strains Grown on Koji and the Umami-Tasting Amino Acid Content of Soy Sauce

We compared the koji-based extracellular carboxymethylcellulases (CM-cellulase), pectinases and xylanases of four Aspergillus oryzae isolates from soy sauce koji, A1, PRB-1 (A2), A3 and A4, with Aspergillus oryzae AS3.951 (A5) via enzyme assays and zymography and determined their correlation to the content of umami-tasting amino acids in high-salt diluted-solid state growth stage leading to soy sauce. In A2 koji, xylanase had the highest activity (28.75 U/g dry weight). Zymogram analysis revealed two different bands of CM-cellulase activity (termed Cel-1 and Cel-2) and one band of pectinase activity (Pec-1) in all koji samples. The intensity of these bands was comparable among all five strains. Interestingly, the same analysis revealed six different xylanase activity bands (termed Xyl-1 to Xyl-6) in all koji samples. After 60 days of cultivation, the free amino acid concentration was highest in soy sauce generated by A4 at 6709.41 mg/100 ml and contained 1690.82 mg/100 ml umami-tasting amino acids (including glutamic acid and aspartic acid), followed by soy sauce generated by A2. Pearson’s coefficient analysis indicated that Xyl-1 and Xyl-2 activities were positively associated with the umami-tasting amino acid content of soy sauce. In conclusion, these data suggested that the xylanases Xyl-1 and Xyl-2 in koji could be important contributors to the umami taste formation of soy sauce.     

米曲霉菌今野菌株所产蛋白酶性质的研究

采用(m)2SO4盐析,再透析提纯得到今野菌株的蛋白酶,该酶热稳定性好,40℃保温5小时,剩余酶活为54%,采用正交试验,得其在反应过程中所受因素影响大小为pH＞酶液浓度＞底物浓度＞温度.酶反应的最适pH为7.0,最适温度为40℃.在以酪素为底物时,该蛋白酶的Km值为6.6‰,NaCl对其有抑制作用.抑制类型为非竞争性抑制.     

蚕豆辣酱的研制

以蚕豆和辣酱为主要原料,利用米曲霉AS3.042、黑曲霉AS3.350、根霉Q303等多种菌种的协同作用,在温度先高后低的条件下固态发酵,所得产品与单一菌种发酵相比,酱香、酯香浓郁,鲜味有明显的提高,氨基酸氮提高了30.2%、全氮提高了11.2%。     

Xi-3米曲霉菌株的保藏与复壮

介绍了Xi-3米曲霉菌株的保藏与复壮的具体做法。采用麸皮保藏法可以使Xi-3米曲霉保藏18年之久且菌种优良性状不变；行之有效的复壮措施，提高了保藏菌株的优良性状和生产性能，为种质资源的可持续发展作出了贡献。     

Characteristics of L-lactic Acid Production byRhizopus oryzae mutant RL6041

A high-yield mutant strain Rhizopus oryzae RL6041 induced by ions implantation was used in the present study. L (+)-lactic acid was generated by RL6041 grown on liquefied corn starch as a substrate. With optimal conditions (Liquefied corn starch 150g/L, (NH₄)₂SO₄ 2.0g/L, MgSO₄·7H₂O 1.0g/L, ZnSO₄·7H₂O 2g/L, KH₂PO₄ 0.2g/L, CaCO₃ 8%, medium size 20/250Ml, seed age 6h, fermentation temperature 38° C), the yield of L (+)-lactic acid in shake-flask reached 133～136g/L after 36h, indicating that the conversion rate was as high as 88%～91%, and the productivity was 3.75g/L·h. There was almost a 70% increase in lactic acid production compared with the original strain RE3303.     

双菌种酿制酱油工艺研究

通过对采用3.042米曲霉和AS 3.350黑曲霉混合发酵酿制酱油工艺的研究,结果表明:80%沪酿米曲霉和20%AS 3.350黑曲霉混合发酵可使成品酱油中的谷氨酸含量提高30%,原料全氮利用率及氨基酸生成率也有所提高,而且色香味也均比单一米曲霉制曲发酵的酱油好.