Growth medium

About: Growth medium is a research topic. Over the lifetime, 1889 publications have been published within this topic receiving 59171 citations. The topic is also known as: culture medium & culture media.

Biosynthesis of branched-chain amino acids in yeast: effect of carbon source on leucine biosynthetic enzymes.

Abstract: The three enzymes in the leucine biosynthetic pathway of yeast do not exhibit coordinate repression and derepression in response to the carbon source available in the culture medium. Growth in an acetate medium results in derepression of the first enzyme in the pathway, alpha-isopropylmalate synthase, and repression of the second two enzymes, alpha-isopropylmalate isomerase and beta-isopropylmalate dehydrogenase, relative to the levels found in glucose-grown cells. The role of endogenous leucine pools as a mediator of these differences was investigated. The leucine pools did not differ significantly between acetate-grown and glucose-grown cells. However, an elevated endogenous leucine pool, caused by exogenous leucine in the growth medium, did decrease the rate of decay of alpha-isopropylmalate synthase activity observed when acetate-grown cells were shifted to glucose. Evidence is provided suggesting that an elevated endogenous leucine pool may increase the in vivo stability of alpha-isopropylmalate synthase under several different conditions. Studies on the kinetics of alpha-isopropylmalate synthase decay in vivo and sensitivity to leucine inhibition indicate that there are two classes of the enzyme in acetate-grown yeast cells.

Thermal tolerance of Talaromyces flavus ascospores as affected by growth medium and temperature, age and sugar content in the inactivation medium

Abstract: Investigations were conducted to determine the influence of growth media, temperature of incubation, age of culture and sugars (sucrose, glucose and fructose) in an apple juice heating medium on thermal tolerance characteristics of Talaromyces flavus ascospores. Of eight culture media tested, carbohydrate-rich formulae supported highest levels of ascospore production. Heat-resistant ascospores developed most rapidly on oatmeal agar, and in all instances increased tolerance to heat was correlated with age of cultures up to 30 d of incubation; little change in heat tolerance was noted as cultures aged from 30 to 58 d. Heat resistance was less when T. flavus was grown at 21 °C compared to 25 and 30°. Protection against thermal inactivation was increased when ascospores were heated in apple juice supplemented with sugars at concentrations sufficient to reduce the aw to 0.96 (60% sucrose, 34.5 % glucose and fructose). This protective effect was not influenced by the type of sugar.

Optimized culture conditions for bacterial cellulose production by Acetobacter senegalensis MA1.

Abstract: Cellulose, the most versatile biomolecule on earth, is available in large quantities from plants. However, cellulose in plants is accompanied by other polymers like hemicellulose, lignin, and pectin. On the other hand, pure cellulose can be produced by some microorganisms, with the most active producer being Acetobacter xylinum. A. senengalensis is a gram-negative, obligate aerobic, motile coccus, isolated from Mango fruits in Senegal, capable of utilizing a variety of sugars and produce cellulose. Besides, the production is also influenced by other culture conditions. Previously, we isolated and identified A. senengalensis MA1, and characterized the bacterial cellulose (BC) produced. The maximum cellulose production by A. senengalensis MA1 was pre-optimized for different parameters like carbon, nitrogen, precursor, polymer additive, pH, temperature, inoculum concentration, and incubation time. Further, the pre-optimized parameters were pooled, and the best combination was analyzed by using Central Composite Design (CCD) of Response Surface Methodology (RSM). Maximum BC production was achieved with glycerol, yeast extract, and PEG 6000 as the best carbon and nitrogen sources, and polymer additive, respectively, at 4.5 pH and an incubation temperature of 33.5 °C. Around 20% of inoculum concentration gave a high yield after 30 days of inoculation. The interactions between culture conditions optimized by CCD included alterations in the composition of the HS medium with 50 mL L− 1 of glycerol, 7.50 g L− 1 of yeast extract at pH 6.0 by incubating at a temperature of 33.5 °C along with 7.76 g L− 1 of PEG 6000. This gave a BC yield of wet weight as 469.83 g L− 1. The optimized conditions of growth medium resulted in enhanced production of bacterial cellulose by A. senegalensis MA1, which is around 20 times higher than that produced using an unoptimized HS medium. Further, the cellulose produced can be used in food and pharmaceuticals, for producing high-quality paper, wound dressing material, and nanocomposite films for food packaging.