摘要:

An electronic control circuit was used to maintain pH within ±0.02 units between successive additions of soluble alkali. Carbon balances show the effects of a series of pH levels and of a range of sucrose concentrations on the proportional yields of end products. There is a marked change in the chemical balance of this fermentation at about pH 7.0, correlated with a suppression of the acetoin enzyme system. Above pH 6.8 a sharp increase in acid production is correlated with decreased formation of diol and carbon dioxide: below pH 6.8 the yield of organic acids decreases steadily. Most efficient conversion to diol occurs from pH 6.0 to 6.4. Several reasons are advanced for selecting pH 6.2 as the optimum. Under anaerobic conditions the fermentation rate is increased over that under aerobic conditions. Diol yields increase and ethanol yields decrease steadily with increasing sucrose concentrations. The increases in diol are accompanied by decreasing yields of organic acids, and not by changes in carbon dioxide production, which remains relatively uniform. The sucrose concentration most efficient for conversion to diol is about 8%, which is dissimilated anaerobically in 30 hr. at pH 6.2 to yield 65 mM. (millimoles) of diol per 100 mM. of invert sugar fermented. Under aerobic conditions the diol–ethanol ratios show a marked increase, and reach a maximum of about 11 at 10% sucrose. This is due largely to increased acetoin and decreased ethanol formation. The dissimilation of 6% sucrose reaches 98% in 71 hr. under aerobic conditions and yields 82 mM. of diol plus acetoin per 100 mM. of invert sugar fermented. The use of either sodium or potassium hydroxide in place of ammonium hydroxide increases five times the period for complete dissimilation of 5% sucrose. Advantages of controlling the reaction by addition of ammonium hydroxide are reviewed.

ISSN:1923-4287    

DOI:10.1139/cjr49f-048

出版商:NRC Research Press    

年代:1949

数据来源: NRC

摘要:

Making use of the quartz frequency standard of the Dominion Observatory crystal clock an electronic frequency converter has been constructed that transforms the 50,000 cycle output of the crystal to a frequency of 60 cycles. Suitable amplification makes possible sufficient power for operating several standard 60 cycle motors and these are being used to drive printing and drum chronographs and for the operation of other types of recorders.

ISSN:1923-4287    

DOI:10.1139/cjr49f-049

出版商:NRC Research Press    

年代:1949

数据来源: NRC

摘要:

Statistical analysis of data obtained with eight commercial electrical moisture meters and 159 samples of Hard Red Spring wheat shows that variations in bushel weight and kernel weight have an effect on the moisture readings but variations in protein and ash content do not. An appreciable amount (from 10 to 30%) of the variation in the G.R.L., Steinlite, Marconi, and Mullard readings is attributable to variations in bushel weight alone; and in the Patterson and Tag–Dielectric readings to bushel weight and kernel weight jointly. The Tag–Heppenstall and Universal meters are not influenced appreciably by the factors investigated.

ISSN:1923-4287    

DOI:10.1139/cjr49f-050

出版商:NRC Research Press    

年代:1949

数据来源: NRC

摘要:

A procedure has been outlined for the estimation of milk lipase. The method is based on the titration of an ether extract of butyric acid derived from the enzymatic hydrolysis of tributyrin under standardized conditions. Some of the fundamental factors involved in the procedure have been discussed. It is suggested that modifications of the method may be used to study lipase activity in other dairy products and in cultures of micro-organisms.

ISSN:1923-4287    

DOI:10.1139/cjr49f-051

出版商:NRC Research Press    

年代:1949

数据来源: NRC

摘要:

A method of estimating bacterial lipase is presented that is believed to be more nearly quantitative than any other at present available. The method is based on the titration of acids in an ether extract of a skim milk culture to following a 30 mm period of lipase activity at 37 °C. It is shown that ether-soluble acids carried into the reaction medium do not interfere with the measurements and that ether-soluble acids are not produced from protein or lactose during the test. The method is applicable over a sufficiently wide pH range to make it generally adaptable in bacteriology.

ISSN:1923-4287    

DOI:10.1139/cjr49f-052

出版商:NRC Research Press    

年代:1949

数据来源: NRC

摘要:

The lipolytic activity in skim milk cultures of micro-organisms representing a number of species and genera were studied by the extraction–titration method described in the preceding paper. No evidence was found of a bacterial lipase having an activity optimum on the acid side of neutrality. No lipase active at approximately pH 5.0 was demonstrated in 20 samples of commercial cheddar cheese of varying age or one sample of blue veined cheese on measurement by the extraction–titration method or by the Petersonet al. method. Weak lipolytic activity was found in one sample of blue veined cheese by the extraction–titration method. No lipolytic activity at pH 8.5 was demonstrated by the extraction–titration method in the one sample of cheese tested at this pH.

ISSN:1923-4287    

DOI:10.1139/cjr49f-053

出版商:NRC Research Press    

年代:1949

数据来源: NRC

摘要:

The lipolytic activity of a strain ofPseudomonas fluorescenswas investigated. Under the investigational conditions activity was greatest when the reaction medium was at approximately pH 8.9 at the start of the reaction period and when the reaction was carried out at approximately 42 °C. The optimum pH for activity by this enzyme was found to be between 8 and 9. This lipase is not specific for tributyrin but hydrolyzes tricaproin and tricaprylin as well, although with decreasing ease. Calcium chloride inhibited rather than enhanced the activity. Lipolytic activity was greater in nutrient broth-base media than in skim milk but the latter was more satisfactory with which to work. Lypolytic activity and fluorescence were not found to be related. Nutrient broth freed of carbohydrate byEscherichia coligrowth and heat-sterilized stimulated production of fluorescence.

ISSN:1923-4287    

DOI:10.1139/cjr49f-054

出版商:NRC Research Press    

年代:1949

数据来源: NRC