I have prepared curdlan (0.5%) containing screening media for screening endo beta- 1,3- glucanase producing Streptomyces colonies. It was prepared by dissolving 0.5gm curdlan (from Sigma) in 0.1N NaOH and then mixed with other media components (yeast extract, peptone, MgCl2.7H2O, KH2PO4, agar) and autoclaved. After autoclaving curdlan showed discoloration (from curdy white to pale brown) and also formed jelly clumps so that uniform spreading of the agar media in the plates was difficult. Kindly suggest any measures to overcome this.
this is what you find immediately by googling "curdlan" (added below): It seems you got irreversible gel formation by heating it too much. It may be difficult to get it sterile if you can not autoclave. You can try sterile filtration (if is not to viscous) or becreative in trying other things (it comes to mind to "wash" the dry curdlan with ethanol or any other microbicidal organic solvent, then evaporate it to produce a "sterile" compound, or you can try to autoclave it in the dry state and solve it later with sterile water, etc.). You also should think over the procedure of solving it in highly alkaline solution (alternative DMSO). If you had used acidic solvent, you certainly would have completely hydrolysed the curdlan to monomers after autoclaving, but I would assume it does not really like being heated in that alkaline solution either. Moreover, this may shift the pH of your entire medium to inhibit growth of your organisms. Another thought would be to grow your colonies first on normal medium and overlay them later with softager containing curdlan.
from the internet:
Functionality
Curdlan gum is tasteless and produces retortable freezable food elastic gels. It is insoluble in cold water a but aqueous suspensions plasticize and briefly dissolve before producing reversible gels (that is, curdling, hence its name) on heating to around 55 °C [504]. Heating at higher temperatures produces more resilient irreversible gels, which then remain on cooling, by the aggregation of the triple-helical structures and syneresis. The 'curds' consist of mixtures of single and triple helices. Salts tend to prevent curdlan from gelling and their presence weakens the final gels [504].
Scleroglucan (from Sclerotinia sclerotiorum) is also a 1 3 β-D glucan but has additional 1 6 β-links that confer solubility under ambient conditions but do not significantly interfere with a triple helix gelling process similar to curdlan. Similar polysaccharides can be also extracted from other sources such as waste yeast.
Interactive structures are available (Jmol). [Back to Top ]
Footnotes
a Curdlan is soluble in dimethylsufoxide [1457].
Thank you Sir.....thank you very much for your valuable information....
- Badges
- Science topic
- Similar topics
- Biological Science
- Biochemistry
- Enzymology
- Enzymes