ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1964.tb04804.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Summary:The classification of 1,466 bacteria, isolated on Yeastrel‐milk agar incubated at 30° from 68 rinses of steam sterilized dairy equipment taken at five farms, showed that micrococci were dominant, with corynebacteria and aerobic sporeforming rods frequent, representatives of these three groups constituting 73% of the isolates. The microflora was characterized by the dominance of organisms which were relatively inactive in milk. Typical milk souring organisms such as lactic streptococci and coli‐aerogenes organisms were rarely isolated, but anaerogenic Gram‐negative rods resemblingAchromobacter, PseudomonasandFlavobacteriumwere not uncommon on milking machine clusters and on a cooling unit. The glass recorder jars contained a relatively high proportion of sporef

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1964.tb04805.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Summary:The incidence of the main types of bacteria among 2,856 isolated on Yeastrel‐milk agar incubated at 30° from 121 rinses of dairy equipment cleansed by chemical methods, showed that micrococci were dominant in low colony count (<104/ft2) rinses of equipment treated by immersion cleaning in caustic soda or cleansed in detergent‐hypochlorite solutions, whereas nonpigmented Gram‐negative rods were dominant in low count rinses of equipment cleansed with detergent‐sterilizers containing quaternary ammonium compounds. Gram‐negative rods were dominant and streptococci frequent in high count (<2·5 × 105/ft2) rinses irrespective of the chemical used. A high proportion of the streptococci and coli‐aerogenes organisms gave acid reactions in litmus milk after 72 h at 22°, many of the anaerogenic Gram‐negative rods and several of the aerobic sporeformers gave proteolytic reactions, whereas the majority of the micrococci, corynebacteria and other asporogenous Gram‐positive rods showed no change. Bacteria isolated from high count rinses were more active in producing milk spoilage reactions at 22° than those isolated f

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1964.tb04806.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Summary:The vitamin requirements ofRhodotorula gracilisare satisfied by inclusion in the growth medium of pantothenic acid and thiamine. For maximum growth in the particular medium and with the size of inoculum used in our experiments a concentration of about 10 μg of pantothenate/1 was sufficient but for rapid early growth a higher concentration was beneficial.Pantothenic acid can be replaced by β‐alanine but maximum growth response then occurs only in the presence of asparagine. Either ammonium sulphate or urea provides a suitable source of nitrogen for growth of the organism.Shake flask experiments with a synthetic medium showed that a solution containing only glucose and phosphate was adequate for fattening, that wide limits in pH value (e.g. 4–8) were permissible and that the rate and efficiency of fat production were not affected by large differences in the concentration of sugar.Provided sugar was still present in the medium a progressive decrease in the percentage of protein was accompanied by a corresponding increase in the percentage of fat in the yeast. When aeration was prolonged beyond the point at which all the sugar was exhausted, this trend was reversed.The fat produced during fattening had a lower iodine value than that produced during normal growth. Only a small proportion of the fat inRh. gracilisis in the free condition and extractable by direct treatment with a simple solvent. Preliminary hydrolysis with hot HCl is necessary for quantitative release of the fat.Refinery cane molasses provides a suitable source of sugar both for growth and for fattening ofRh. gracilis. Growth in a fermentor with incremental feeding, under conditions of high aeration and rapid stirring, gave a yield of dry yeast equivalent to 52–54% of the sugar consumed; the doubling time during the logarithmic growth phase was 3 h.Aeration ofRh. gracilisin a phosphate‐molasses medium resulted in a rapid consumption of sugar during the whole period of aeration. This was accompanied by an increase in the weight of yeast, accounted for by an increase in all constituents—fat, carbohydrate, mineral matter and a small amount of protein formed from the residual nitrogen carried over from the growth medium. Since much more fat than protein was produced the percentage of fat in the yeast rose and the percentage of protein fell. The proportion of carbohydrate in the cell was subject to some fluctuation. Under certain conditions it appears that the reserves of carbohydrate may be drawn upon to provide energy for fat formation, resulting in an actual destruction of cellular carbohydrate.The proportion of sugar converted to fat rose to a maximum betweenc.14–23 h and then rapidly declined. For a short period a fat coefficient of over 40% was attained in one experiment. Thereafter conversion was relatively inefficient, a small quantity of fat being produced from the consumption of a large quan

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1964.tb04807.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1964.tb04808.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Summary:In experiments with a surface film test it was found that variation of certain test conditions affected the relative activity of two detergent‐sterilizer formulations. It was also found that to achieve a high degree of reproducibility in the residual count on a treated surface from one occasion to another, it is necessary to control closely the numbers of bacteria present in the dried milk fil

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1964.tb04809.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Summary:In the Netherlands the disintegration of processed strawberries, accompanied by unpleasant odour and flavour, is generally caused by the mouldByssochlamys nivea. Pectolytic enzymes produced during the growth of the mould are responsible for the disintegration. The organism is not killed by the heat treatment normally applied to strawberries.

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1964.tb04810.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Summary:Heat resistant moulds of the generaByssochlamys, Aspergillus, PenicilliumandPaecilomycescan be cultivated selectively in the presence ofBacillusspp. when at least 10 p/m of chloramphenicol or chlortetracycline is added to the growth medium. The inhibitory agents sulphafurazole, penicillin, streptomycin, oxytetracycline and furazolidone, do not give completely selective and optimal growth of these moulds. Selective cultivation of heat resistant moulds from 200 samples of Dutch soil showed thatByssochlamys niveaoccurs more frequently than was expected, whereasByss. fulvaoccurs by way of exception. Other heat resistant moulds observed in soil are, in order of frequency, species of the generaAspergillus, PaecilomycesandPenicillium.

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1964.tb04811.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Summary:The present report gives the results of the effect of 10 bacteriophages ofSerratia marcescenson 107 strains of the genusSerratia. The phage S103 was the most effective (80% strains lyzed), and the phage PK the least (12% strains lyzed). Only 13 strains were resistant to all the phages studied. The majority of the strains of the genus studied could be allocated to one of seven groups on the basis of their sensitivity to the phages.

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1964.tb04812.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Summary:Various media selective for potential food poisoning staphylococci have been investigated to determine the most suitable ones for use with fish. These were then used with 161 samples of fish and fish products simultaneously with estimations of viable bacterial counts and of the numbers of coli‐aerogenes organisms. Attempts to isolate salmonellae from these were also mad

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1964.tb04813.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY