摘要:

SUMMARY:In detailed studies of the growth ofAspergillus ustus, Penicillium oxalicum, P. frequentansandP. notatumin whey with fat production in view, the first two showed the highest lactose utilization and felt weights in shaken cultures while the last two gave as good or better felt yields in stationary cultures.When A.ustuswas grown in shaken culture in whey with and without the addition of 1·14 g/1. of ammonium nitrate, the extra nitrogen led to the production of larger amounts of fat, butP. frequentansdid not form additional fat in these circumstances.A. ustuswas the best mould; in whey plus ammonium nitrate it utilized up to 96% of the lactose and formed, per litre of whey, about 17 g of mycelial felt containing 13% of protein and 28% of fat

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1959.tb00150.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

SUMMARY:The suitability, as indicators of the faecal contamination of foods, of two types of obligately anaerobic nonsporeforming bacteria which are very numerous in faeces, viz. members of the generaBacteroidesandBifidibacterium, was tested. For the counting ofBacteroides, Beerens’bile‐azide agar (1957) enriched with 10% (v/v) of blood, and incubated in oval cross section tubes, was found useful.Bifidibacterium could be counted very well in Frisell's tomato‐azide agar (1951), incubated in the same way. Both media being not too selective, confirmation of representative numbers of colonies was necessary. After microscopical examination, the biochemical study of properties such as catalase reaction, oxygen tolerance, carbohydrate fermentation and nitrate reduction may be required.The 3Bacteroidesstrains tested died off rather rapidly when present in sterile ice cream under conditions where Enterobacteriaceae and faecal streptococci increased in numbers. Accordingly they were never found in considerable numbers in some 25 samples of food which appeared to contain very high numbers of other bacteria of faecal origin. The 8Bifidibacteriumstrains investigated appeared more resistant. However, under conditions permitting growth, they increased less than the Enterobacteriaceae and faecal streptococci; and where the latter did not increase but did survive, theBifidibacteriumdecreased in numbers. In line with these findingsBifidibacteriumwas not even found in numbers of the order of 10/g in the 25 samples of food mentioned above. NeitherBacteroidesnorBifidibacteriumcan therefore be considered suitable as an indicator of the contamination of foods with bacteria of faecal origin and of the subsequent growth of these bacteria th

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1959.tb00151.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

SUMMARY:From the mortality curves ofEscherichia colicells heated at 55° in Ringer's solution both Decimal Reduction Times (DRTs) and 99–9% mortality times were obtained. In terms of these measures of heat resistance, cells harvested from broth cultures 0–8 hr old were more susceptible than those from more mature cultures. The time of commencement and the approximate duration of the logarithmic phase of growth of the organism in broth were determined from growth curves, and it was observed that the heat resistance was minimal during that phase.Death rates were not always uniform for the whole of a given population. Particularly among young cultures, a period of rapid death was frequently followed by the slower death of a relatively small number of survivors. In one instance only was an initial period of slow death followed by one of more rapid d

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1959.tb00152.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

SUMMARY:Mixed cultures of bacteria grown in spent gas liquor readily oxidized phenol,o‐,m‐ andp‐cresol, catechol, 3‐methyl catechol, 4‐methyl catechol, resorcinol, 2‐methyl resorcinol, and 4‐methyl resorcinol. Quinol, pyrogallol and phloroglucinol were more resistant. The optimum temperature was 30° and the best pH range 6·5–7·8. Yeast extract and sterile sewage sludge both increased the rate of growth of organisms in liquor when the inoculum was small. Five phenol oxidizing organisms were isolated in pure culture. Copper in concentrations greater than 1 p/m inhibited both growth and phenol oxidation by one of these.Mixed cultures grown in an ammonium thiocyanate medium originally inoculated withThiobacillus thiocyanoxidansoxidized potassium thiocyanate and sodium thiosulphate. Chloride inhibited thiocyanate oxidation in concentrations above 5,000 p/m, although adaptation to 15,000 p/m was possible. Phenol inhibited thiocyanate oxidation in concentrations of 300 p/m or more. Mixed cultures grown on sodium thiosulphate oxidized sodium trithionate and tetrathionate, potassium pentathionate and hexa‐thionate, and potassium and ammonium thiocyanateManometric determinations of the 5 day biological oxygen demand of effluents after treatment showed good agreement with the values obtained by the conventional method, the manometric values being usu

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1959.tb00153.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

SUMMARY:The bacteriology of the root region of oat plants grown under controlled conditions has been studied by means of improved techniques for separate estimation of the microfloras of the rhizosphere soil and of the root surface. The plate count of bacteria in the root region increased during the growing period of the plants; superphosphate produced a greater increase, which was probably due to increased plant growth, as no such effect was observed in uncropped soil.The numbers of acid producing and dicalcium phosphate dissolving bacteria were increased in the root region, but the latter were not preferentially stimulated. Dressings of superphosphate and dicalcium phosphate also did not preferentially stimulate either group. No evidence was obtained, by the plate method used, of the presence of organisms capable of dissolving variscite, strengite, or gafsa rock phosphate, although the plants showed appreciable response to gafsa rock phosphate.

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1959.tb00154.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

SUMMARY:Over a hundred isolates which produced haloes around their colonies on dilution plates containing calcium carbonate or dicalcium phosphate have been obtained in pure culture from the root region of the oat plant. Of these, more than 50% were pleomorphic, and this group had the highest proportion of isolates which could produce clear zones on agar media containing either calcium carbonate, dicalcium phosphate, tricalcium phosphate, freshly precipitated hydroxyapatite or basic slag. None of the isolates showed dissolving ability on agar media containing gafsa rock phosphate, variscite, strengite or taranakite. However, when an analytical method was used, 82% of the isolates tested proved able to release phosphate from gafsa rock phosphate, though to a much lesser extent than from dicalcium phosphate. None of the isolates tested by this method released phosphate from variscite, strengite or taranakite.The nature of the organic acids produced from glucose by 26 of the isolates was also investigated. The majority produced mainly lactic acid, but a few also gave an acid with chromatographic properties similar to those of 2‐keto‐gluconic a

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1959.tb00155.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

SUMMARY:To select and count the sugar tolerant yeasts which ferment sixfold concentrated orange juice, a high sugar agar medium was developed which contains 50% of glucose, 1% of citric acid and 1% of Tryptone; it is incubated for 4–5 days at 25°.The medium has disadvantages: it is troublesome to prepare, and colonies grow slowly and are translucent. These properties result directly' from the high sugar concentration, on which the selective action of the medium depends.Counts on this medium have been compared with those on potato dextrose or nutrient dextrose agars (with 2% and 1% of glucose respectively), with yeasts isolated from fermenting concentrate, in pure culture, and under various practical conditions. As a rule, the counts were virtually the same on the different media; nutrient dextrose agar occasionally failed to record small numbers of these yeasts. If the two low sugar media were acidified to pH 3·5 the counts were reduced.Potato dextrose agar recorded, besides the above yeasts, sugar intolerant yeasts entering from dirty machines or through bad canning practice: nutrient dextrose agar recorded bacteria in addition. The difference between parallel plating on these media and on the high sugar medium thus yielded useful information about sources of casual contamination.It is suggested that the above would also be largely applicable to other sugar‐rich concentrates of not less than 50

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1959.tb00156.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

SUMMARY:Composite morning milk samples were taken once weekly for 9 weeks from 24 dairy farms. In all 208 samples were tested, and coagulase positive staphylococci (aureus, albusandcitreus) were isolated from 127 (61%). The week by week recovery of these staphylococci from individual farm samples varied between 11% and 88% Penicillin resistant coagulase positive strains were recovered from 20 samples (10%).

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1959.tb00157.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

SUMMARY:The resistance to drying under atmospheric conditions ofEscherichia colicells suspended in water, broth and horse serum was investigated. Cells from cultures in the early (logarithmic) growth phase were more susceptible than older cells, and this, together with the fact that the strain ofE. coliused was very sensitive to drying, even in a protective menstruum such as horse serum, made it unlikely that the clearer chromatin staining obtained with cells from young than from old cultures could be attributed to the occurrence of less disruption of the former during drying of the films.

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1959.tb00158.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

SUMMARY:A study has been made of the effectiveness of an Ibcol‐triethylene glycol mixture for either atmospheric or surface disinfection in various types of poultry premises. Only a moderate bactericidal action was obtained with atmospheric disinfection usingE. colias the test organism. With a stronger mixture, a complete kill was obtained for surface disinfection with overnight exposure but the reduction in numbers of the test organisms with 30 min exposure did not exceed 75% in any experiment. Very satisfactory results were obtained with a formalin‐water aero

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1959.tb00159.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY