摘要:

Recombinant DNA methods were used to begin a molecular biological study of the biotechnically important lipase produced by the fungusRhlzopus delemar.Pure, high molecular weight DNA was isolated, mildly digested withMboI, ligated into pBR322, and introduced intoE. coliby transformation. Transformants were recovered by ampicillin selection. The frequency of insertional inactivation of tetracycline resistance in the transformants was 95%. The cloned DNA inserts ranged in size from approximately 0 to 14 kilobases (average: 4.7). Colony hybridization using fungal genomic DNA as a probe verified the presence of fungal sequences in the transformed cells. A rapid, sensitive assay for lipase production was developed and applied to a sufficient number of transformants to represent several genomic equivalents of fungal DNA. No lipase‐producing clones were detected.

ISSN:0890-5436    

DOI:10.1080/08905439009549780

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The extracellular polysaccharide formed byPhysarum polycephalumduring spherulation was produced by fermentation. Both cell yields and polysaccharide formation were adversely affected by the presence of ambient incident light. Crude polysaccharide was fractionated with acetone into two fractions (I, II). Fraction I was viscous and contained 3.5% sulfated and 0.5% phosohorylated sugar residues. The non‐viscous Fraction II contained 0.4% sulfated and 22% phosphorylated sugar residues. Fraction II formed gels at pH>8.5 with calcium, magnesium, iron and zinc ions. Fraction I and unfractioned polysaccharide did not form gels under any conditions tested.

ISSN:0890-5436    

DOI:10.1080/08905439009549781

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Enzymes are often thought of by the food processing industry as detrimental, to be destroyed by heat treatment. This is based on undesirable changes in texture, color, flavor, aroma and nutrition that may occur on harvest and storage. However, the uses of enzymes in brewing, cheese manufacture, meat tenderization, baking and protein hydrolysis are well known, having been used for many years. Of more recent utilization are enzymes for making glucose and fructose from starch, for separating racemic mixtures of D‐and L‐amino acids, for cleaning of processing equipment, for changes in functionality of high protein foods and increasing juice yield and clarity.

ISSN:0890-5436    

DOI:10.1080/08905439009549782

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The historical use of enzymes for food processing is briefly reviewed. The manufacturing process of microbial food enzymes is described including the fundamental purity criteria recommended by Joint FAO/WHO Expert Committee on Food Additives (JECFA) and Food Chemicals Codex. Principles for safety evaluation focus on the possible presence of toxic contaminants in the commercial enzyme preparation. Possible sources of any undesirable contaminants include the raw materials used, the properties of the production strain, contamination with foreign micro‐organisms, use of additives and processing aids in recovery of the enzyme. Systems for design of toxicology programmes are reviewed. A case study is given summarizing the safety evaluation of an immobilized lipase used for the interesterification of fats and oils. Based upon a no‐effect level derived fromin vitroand animal feeding studies it is concluded that the enzyme is safe for the intended use.

ISSN:0890-5436    

DOI:10.1080/08905439009549783

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The relationship between pyruvate utilization and acetoin production was elucidated by incubatingLactobacillus plantarumcells in buffered reaction mixtures which contained varying concentrations of pyruvate, glucose, and metabolic inhibitors. Pyruvate utilization was greatest at pH 4.5, was pseudo‐first order with regard to pyruvate concentration, and was stimulated by glucose. Fructose, galactose, sucrose and lactose were also stimulatory, but maltose was not. The molar conversion efficiency for pyruvate to acetoin was 72–84% at pH 4.5, but only 37–45% at pH 5.5. Pyruvate utilization decreased when the metabolic inhibitors N,N’ dicyclohexylcarbodiimide, carbonylcyanide m‐chlorophenylhydrazone or 2,4 dinitrophenol were added to the buffers. These data suggests that energy, possibly in the form of proton motive force, is required for pyruvate utilization inL.plantarum.

ISSN:0890-5436    

DOI:10.1080/08905439009549784

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0890-5436    

DOI:10.1080/08905439009549785

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0890-5436    

DOI:10.1080/08905439009549779

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor