基于酵母表面展示技术的基因工程活载体疫苗，在鱼类疫苗的研究中至今未见报道。海水鱼类病原菌哈维氏弧菌的溶血素是其主要的毒力因子之一，为制备以酒精酵母为载体的基因工程疫苗，参照其Genebank中基因序列设计一对引物，PCR扩增得到预期长度的产物，双酶切插入用于酒精酵母表面展示的穿梭质粒载体pYD1，转化大肠杆菌TOP10，提取阳性质粒转化酒精酵母菌株EBY100，诱导表达后，用免疫荧光和流式细胞仪检测外源蛋白的表达，结果测得最佳诱导时间为36-48小时，诱导培养后约30.0%左右的酵母细胞表达外源蛋白；同时以EBY100和转空质粒的酵母菌株为对照，测得诱导培养后的阳性酵母转化株的细胞对牙鲆鱼血细胞具有溶血活性，以此酵母活细胞分设高中低三个深度组，腹腔注射养殖牙鲆幼鱼，检测其毒性，结果表明此重组酵母对牙鲆是安全的。为下一步鱼用活载体疫苗免疫效果的研究奠定了基础。

Trehalose accumulation from starch by Saccharomycopsis fibuligera sdu was examined in 300-ml shaken flask culture and Biostat B2 2-1 fermentation. In the 300-ml flask, 16.5% (w/w) trehalose accumulated in the yeast cells (cell dry weight) was observed with 100-ml medium shaken at 200 rpm for 50 h at 30

HL1 gene encoding haemolysin from Vibrio harveyi SF-1 was expressed in yeast cells and the expressed haemolysin was displayed on the cell surface. After induction for 36 h in galactose-containing medium, one-third of the cells contained the displayed protein and the displayed cells had haemolytic activity on erythrocytes from flounder. The double diffusion agar analysis showed that the sera from the flounder immunized with the displayed yeast cells having the haemolytic activity could form precipitate with the purified haemolysin. ELISA analysis indicated that immunization times had great influence on increased production of the specific antibody against haemolysin in turbot immunized with the displayed yeast cells having the haemolytic activity. After the challenge with V. harveyi SF-1, it was found that earlier protection in flounder and significant protection in turbot, both of which were immunized with the displayed yeast cells having the haemolytic activity, were achieved. These results suggested that the displayed yeast cells with the haemolytic activity could be used as potential live vaccine in marine fish.

In this study, the effects of inositol addition on expression of the MAL gene encoding maltase and phosphatidylinositol (PI) biosynthesis in Schizosaccharomyces pombe (a naturally inositol-requiring strain) were examined. We found that specific maltase activity was at its maximum when the concentration of added inositol reached 6 ug ml1 in a synthetic medium containing 2.0% (w/v) glucose. When the concentration of added inositol was 1 ugml1 in the medium, repression of MAL gene expression occurred at glucose concentration higher than 0.2% (w/v). However, when S. pombe was cultured in the synthetic medium containing 6 ug ml1, repression of maltase gene expression occurred only at initial glucose concentration above 1.0% (w/v). More mRNA encoding maltase was detected in the cells grown in the medium with 6 ug ml1 inositol than in those grown in the same medium with 1 ug ml1 inositol. These results demonstrate that higher inositol concentrations in the synthetic medium could derepress MAL gene expression in S. pombe. PI content of the yeast cells grown in the synthetic medium with 6 ug ml1 of inositol was higher than that of the yeast cells grown in the same medium with 1 ug ml1 of inositol. This means that PI may be involved in the derepression of MAL gene expression in S. pombe.

Cyanothece sp. 113, a unicellular, aerobic, diazotrophic and photosynthetic marine cyanobacterium, produced 22.34 g/l of exopolysaccharidein 11 days at 29℃, aeration rate of 7.0 l/min and continuous illumination with 4300 lux. After purification, the spectra of UV, IR, 1H NMR, 13C NMR and GC–MS analysis showed that the purified exopolysaccharide was a-D-1,6-homoglucan. This is first report describing linear a-D-1,6-homoglucan exopolysaccharide produced by marine cyanobacteria.