正烷酵母的营养评价

1.本实验所用正烷酵母(假丝酵母Y-17)的营养素含量与国外同类产品相仿。铅、砷、汞、苯并(a)芘含量均在联合国系统蛋白质顾问小组规定的范围之内,正烷烃及总芳烃含量除部分样品稍高外亦均在该范围之内;是一个有前途的饲料蛋白质补充品。 2.测得各样品的PER值为:正烷烃不脱酵母(不脱)1.18;脱脂脱核酸酵母(双脱)1.617药用酵母1.52;全脂黄豆粉1.81,不脱酵母显著低于其他样品。于饲料中补充了0.3％DL-蛋氨酸后校正PER上升为:不脱酵母2.32;双脱酵毋2.49;药用酵母2.35;全脂黄豆粉2.28。校正用的标准品为经ANRC参考蛋白(PER为2.50)标定的国产酪蛋白,其校正PER值为2.43。 3.以含25％、35％不脱酵母和25％双脱酵母的饲料喂养断乳大白鼠一年。以常备饲料和25％的药用酵母饲料为对照。前三个月雄鼠的平均增重和进食量以常备组最好,其次是药用酵母和双脱酵母,25％和35％不脱酵坶组最差。这三组问差异显著;雌鼠对不同饲料的反应不敏感,三个25％酵母组的增重和进食量都没有显著差异,但均低于常备饲料组,在后9个月无论雌雄鼠各酵母组与常备饲料组动物的增重间不再存在统计差异,这表明这几种酵母饲料对维持成年鼠的营养效果基本上是一致的。在试验之初和结束时测大鼠血红蛋白、红细胞、白细胞、血清谷丙转氨酸、血清胆固

EVALUATION OF NUTRITIVE VALUE OF N-ALKANE GROWN YEAST

1.The nutrient content of yeast (Condida Y-17) grown on n-alkane studied in this experiment was comparable to that of the same type of yeast produced in other countries. Its content of lead, arsenic, mercury and benzo (a) pyrene were within the limit proposed by the Protein-Calorie Advisory Group of the United Nations System. The Content of its residual n-alkanes and total aromatic hydrocarbons were within or a little over that limit. It is a good supplementary protein feed.2.The corrected PER values were, yeast grown on n-alkane 1.18; deli pid and denucleic acid yeast grown on n-alkane 1.16; brewer's yeast 1.52; full fat soybean meal 1.81. The PER of yeast grown on n-alkane was significantly lower than those of other samples. When 0.3% DL-methionine was added to the diet, the corrected PER values increased: n-alkane grown yeast 2.32; delipid and denucleic acid n-alkane grown yeast 2.49; brewer's yeast 2.35; full fat soybean meal 2.28. The corrected PER value of casein used for correction was 2.43, it was standardized with ANRC reference protein (PER = 2.50).3.Yeast grown on n-alkane with and without removal of lipids and nucleic acid was fed to groups of rats at a dietary level of 25% and 35% respectively for 1 year. A stock diet group and a brewer's yeast diet group were used as control. In the first 3 months the weight gain and feed consumption of the rats fed n-alkanc grown yeast diet were lower than those of the two control groups. The male rats were more sensitive to the change of diet. In the later 9 months the difference of weight gain among different groups were not significant. The concentration of haemoglobin, red cell counts, white cell counts, GPTase activity, serum cholesterol levels and serum urea levels determined at the beginning and the end of the experiment were all in the normal ranges. The concentrations of n-alkanes and odd-chain fatty acids in the adipose tissue of the n-alkane grown yeast group were higher than those of the two control groups, and the difference was highly significant. The concentrations of total aromatic hydrocarbons and benzo(a) pyrene in the muscle of different groups of rats were 0.4-0.6 ppm and 0.4 ppb respectively. No detrimental effect was observed in pathological examination.4.When 5% fish meal or 3.5% casein was added to the 25% n-alkane grown yeast diet, the weight gain and feed consumption of weanling rats were improved significantly, though it was still inferior to those fed with stock diet.5.Strongly growth depressive effect was noted as the level of n-alkane grown yeast was increased to 20% in the diet. This depressive effect was neither due to the toxicity of the residual n-alkanes and aromatic hydrocarbons, nor due to the deficiencies of potassium and selenium in the diet. It might be the result of nutrient or nutrients imbalance of the diet. The appropriate amount of yeast grown on n-alkane used in mixed feed should not be more than 15%.