Growth models of cultures with two liquid phases. III. Continuous cultures

Some mathematical models, which have been used to describe batch growth in fermentations with two liquid phases present, are used to predict the behavior of continuous fermentations in a chemostat. Two types of dispersed systems are considered in this investigation. In the first, type, it is assumed that the composition of the dispersed phase is such that, increased substrate utilization results in a decreased substrate concentration with no change in the interfacial area. In the second type of system, the dispersed phase is assumed to be pure substrate; therefore, the substrate concentration in the dispersed phase remains constant but the interfacial area is affected by changes in dilution rate. Three special cases are examined for each type of system in order to examine the effect of the interfacial area, the phase equilibrium constant, and the mass transfer coefficient on system performance. Comparison of two of the models with available experimental data shows fair agreement, between model and data.     

Lipids in plant tissue cultures. III. Very long-chain fatty acids in the lipids of callus cultures and suspension cultures

The lipids in plant tissue cultures contain in addition to the common saturated and unsaturated fatty acids even- and odd-numbered fatty acids having chain-lengths up to 26 carbon atoms.     

Lipids in plant tissue cultures IV. The characteristic patterns of lipid classes in callus cultures and suspension cultures

Lipids from callus cultures and suspension cultures of higher plants constitute 5 to 8% of the dry tissue's weight.The predominant lipid classes are the sterols, steryl esters, steryl glycosides and esterified steryl glycosides. Considerable amounts of a variety of sterylglycolipids, whose structures are not completely elucidated, are also present. Triglycerides and phospholipids occur in small proportions, whereas monogalactosyl diglycerides, digalactosyl diglycerides and sulfoquinovosyl diglycerides are present only in traces, if at all.β-Sitosterol is the predominant constituent sterol, stigmasterol and campesterol as well as a variety of as yet unidentified sterols occur in smaller proportions. The major constituent fatty acids are palmitic, oleic, linoleic and linolenic acids. Saturated very long-chain fatty acids are found in smaller proportions. Unusual fatty acids, such as epoxy acids, which occur in the seed lipids of certain plants, are not found in tissue cultures derived from these plants. Clucose and traces of galactose are the only sugars obtained by acid hydrolysis of the glycolipids occurring in plant tissue cultures.     

Bacterial breakdown of benomyl. II. Mixed cultures

Experiments with mixed bacterial cultures grown in liquid media which contained the benzimidazole fungicide benomyl, with or without Na-lactate, as source of carbon provided circumstantial evidence for cleavage of the benzimidazole heterocyclic ring. Yet, neither 2-aminobenzimidazole (2-AB) nor benzimidazole, as sole source of carbon, supported any bacterial growth. Total ¹⁴C-balance analysis experiments conclusively showed production of ¹⁴CO₂ from [2-¹⁴C] methyl benzimidazol-2-yl carbamate (MBC), and thus cleavage of the benzimidazole nucleus; bioassays, however, showed that the actual rate of benomyl and MBC breakdown was only small, the parent compound benomyl being still recovered in substantial quantities after up to 80 days of incubation. Therefore, cleavage of the benzimidazole ring is probably a matter of cometabolism, n-butylamine which originates from the butylcarbamoyl side chain serving as the proper source of carbon.Besides radiolabelled 2-AB and CO₂, an unknown metabolite was isolated which showed characteristics of a 2-AB-nucleotide. Probably, 2-AB was incorporated into bacterial DNA, which upon lysis of the bacterial cells gave rise to the nucleotide in question. Therefore, 2-AB might exert its inhibitory action by interfering with the normal functioning of DNA.     

Lipids in plant tissue cultures. II. Unusual fatty acids in lipids of Hydnocarpus anthelminthica cultures

The lipids in callus cultures of Hydnocarpus anthelminthica were studied after 60, 160 and 460 days of growth. In each of the cultures the lipid classes usually found in plant tissue cultures were detected. With increasing age of the cultures the total lipid content as well as the proportions of triglycerides decreased. The major constituent fatty acids of the total lipids were palmitic and linoleic acids. Small amounts of cyclopentenyl fatty acids were also present. The proportions of saturated straight-chain fatty acids increased with the age of the cultures whereas the proportions of monounsaturated straight-chain fatty acids decreased. Only small changes were observed with polyunsaturated fatty acids. The content of cyclopentenyl fatty acids rose with the age of the cultures. The monounsaturated straight-chain fatty acids consisted of mixtures of isomers whose composition changed with the age of the cultures. In contrast, the polyunsaturated straight-chain fatty acids belonged exclusively to the Δ9 series, regardless of the age of the cultures.     

Bacterial breakdown of benomyl. I. Pure cultures

With different soil and water samples as inoculum and the benzimidazole fungicides benomyl (either as Benlate or as the pure compound) and thiabendazole as selective agents, a large number of, mainly fluorescent, Pseudomonas strains were isolated which nearly all were able to grow in a mineral medium with benomyl as the sole source of carbon. However, no growth occurred with any of a series of other benzimidazole compounds, viz. benzimidazole, 2-aminobenzimidazole (2-AB), thiabendazole and fuberidazole. Although benomyl—or rather its non-enzymatic breakdown product methyl benzimidazol-2-yl carbamate (MBC)—was partially degraded to 2-AB, most probably n-butylamine, which arises after splitting off of the butylcarbamoyl side chain, was the actual carbon source for the Pseudomonas isolates.When incorporated in a lactate medium, 2-AB markedly inhibited the growth of Pseudomonas spp. at a concentration of 250 g/ml, with complete inhibition being attained at 500 g/ml. For Bacillus spp. grown in liquid peptone media benzimidazole compounds were inhibitory at concentrations of 500–1000 g/ml, with a toxicity increasing in the order: benzimidazole 相似文献   

Polyamines in rat hepatocyte cultures.

In rat hepatocytes cultured for 120 h polyamine content was markedly modified. Putrescine concentration reached a maximum at 48 h, spermidine increased for 48 h and then remained constant, spermine after a decrease returned to its initial values. Total polyamine amount was increased by 75%. Both ornithine decarboxylase and the retroconversion pathway were responsible for these modifications. The possible correlation between polyamine metabolism and retrodifferentiation process was investigated by studying them in conditions which are known to preserve differentiated functions.     

Human testicular cultures. II. Sertoli cells.

Two cell types, one epitheloid and the other fibroblast-like, were found in human testicular cultures derived from testes of patients. Ultrastructural studies indicated that, whereas the epitheloid cells were Sertoli cells, the fibroblast-like cells were fibroblasts. The Sertoli cells could maintain growth for a period of more than 4 months. In cultures derived from normal testes, only fibroblasts were observed.