Onishi N, Yamashiro A, Yokozeki K
Central Research Laboratories of Ajinomoto Co. Inc., Kawasaki-shi, Japan.
Appl Environ Microbiol. 1995 Nov;61(11):4022-5. doi: 10.1128/aem.61.11.4022-4025.1995.
Our stock cultures were screened for microorganisms that can produce galacto-oligosaccharide (Gal-OS) from lactose. Of the 574 strains of bacteria and yeasts tested, Sterigmatomyces elviae CBS8119, Rhodotorula minuta IFO879, and Sirobasidium magnum CBS6803 were found to be efficient producers of Gal-OS from lactose and S. elviae CBS8119 was selected as a representative, high-level producing strain. With toluene-treated resting S. elviae CBS8119 cells, 135 mg of Gal-OS per ml was produced from 360-mg/ml lactose. During this reaction, the by-product glucose was found to inhibit Gal-OS production. Therefore, in order to remove the glucose from the reaction mixture, a culture method in which cell growth followed the enzymatic reaction was devised, which increased the yield of Gal-OS considerably because of the consumption of glucose for cell growth. Under such conditions, 232 mg of Gal-OS per ml was produced from 360-mg/ml lactose after incubation at 30 degrees for 60 h. The structure of the major product was identified as O-beta-D-galactopyranosyl-(1-->4)-O-beta-D-galactopyranosyl-(1-->4)-D- glucopyranose (4'-galactosyl-lactose) by 13C nuclear magnetic resonance spectroscopy.
我们对保藏培养物进行了筛选，以寻找能够从乳糖生产低聚半乳糖（Gal-OS）的微生物。在测试的574株细菌和酵母菌株中，发现埃氏掷孢酵母CBS8119、微小红酵母IFO879和大孢西罗酵母CBS6803是从乳糖高效生产Gal-OS的菌株，其中埃氏掷孢酵母CBS8119被选为具有代表性的高产菌株。用甲苯处理过的埃氏掷孢酵母CBS8119静止细胞，以360mg/ml乳糖为原料，每毫升可生产135mg Gal-OS。在该反应过程中，发现副产物葡萄糖会抑制Gal-OS的产生。因此，为了从反应混合物中去除葡萄糖，设计了一种细胞生长跟随酶促反应的培养方法，由于细胞生长消耗了葡萄糖，Gal-OS的产量大幅提高。在这样的条件下，360mg/ml乳糖在30℃孵育60小时后，每毫升可产生232mg Gal-OS。通过13C核磁共振光谱法确定主要产物的结构为O-β-D-吡喃半乳糖基-(1→4)-O-β-D-吡喃半乳糖基-(1→4)-D-吡喃葡萄糖（4'-半乳糖基乳糖）。
