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Do Coletivo Para o Individual/Coletivo (A9)

 

 

 

 

 

 

Semeadura de Orquideas: OMNISTERRA

http://www.omnisterra.com/botany/cp/slides/tc/tc.htm

MICROWAVE STERILIZATION OF TISSUE CULTURE MEDIA

Authors:	E.M.A. Youssef, G.A. Amin
Keywords:	microwave-oven, Populus alba, in vitro, micropropagation
Abstract: Culture media microwaved for 15 min at 390 W or for 5, 10 or 15 min at 520 W gave 96%-100% sterilization rates and totally inhibited the growth of Bacillus subtilis, B. megatherium and B. coagulans. Explants of Populus alba grown on medium exposed to 260 W microwave for 5 min showed the highest frequency of survival and shoot proliferation, while those cultured on medium treated with 520 W for 10 min resulted in the tallest shootlets and greatest number of leaves per shootlet. Although the rooting response and number of roots formed per shoot explant were similar on microwave- or autoclave- treated media, the longest roots occurred on media microwaved for 15 min at 130 W or for 10 or 15 min at 390 W or 520 W.

Source: http://www.actahort.org/members/showpdf?booknrarnr=560_104 on May 7, 2012.

Microwaves in the laboratory: effective decontamination.

Border BG, Rice-Spearman L.

Source

Department of Diagnostic and Primary Care, TTUHSC, Lubbock 79430, USA. alhbb@ttuhsc.edu

Abstract

OBJECTIVE:

We hypothesize that microwave irradiation of certain contaminated materials typically used in a clinical laboratory or a home healthcare setting could produce efficient and effective sterilization when compared to standard autoclave methods.

DESIGN:

A standard household carousel microwave oven unit used at the High setting was employed to expose certain materials that had been contaminated with either bacteria or yeast to microwaves for specific intervals of time. Following each time interval, materials were checked for effectiveness of decontamination using standard culture techniques and colony counting. Additionally, powdered media was prepared and microwave irradiated for specific times. The media was then poured into plates and checked for microbial contamination; another set of plates was examined to determine the ability of the irradiated media to support bacterial growth.

SETTING:

This study was carried out at Texas Tech University Health Sciences Center in Lubbock TX.

MAIN OUTCOME MEASURE:

Standard culture and colony counting techniques were used to determine the efficacy of microwave sterilization.

RESULTS:

The study indicated that microwave irradiation provided effective and efficient sterilization of all materials tested. Of the bacteria studied, only E. coli survived beyond 30 seconds of microwave exposure. Yeast did not survive beyond 15 seconds of microwave exposure. Swabs and gauze contaminated with bacteria or yeast were completely sterilized after 30 seconds. After three minutes in the microwave oven, powdered, prepared media was free of contamination while able to support growth when inoculated with S. aureus.

CONCLUSION:

We conclude that a household carousel microwave oven unit can provide fast, effective sterilization of certain contaminated materials typically used in a clinical laboratory, student laboratory, or home healthcare setting.


FONTE:  http://www.ncbi.nlm.nih.gov/pubmed/10539102?ordinalpos=10&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum MAY 4, 2012 at 22:43 hours

Microwave Oven Irradiation as a Method for Bacterial Decontamination in a Clinical Microbiology Laboratory

FONTE :http://jcm.asm.org/content/6/4/340.full.pdf MAY 4, 2012 at 22: 35 hours.



Bacterial decontamination of food products after exposure to microwave oven irradiation has been well documented, as reviewed by Culkin and Fung (2).
Although experiments done by Culkin with Escherichia coli and Salmonella typhimurium suggest that heat alone did not cause the lethality associated with microwave irradiation, definitive experiments by Goldblith and Wang (3) determined that the lethal effects of microwaves could be prevented by keeping the test organisms in an ice bath during exposure. Additional experiments conducted by Lechowich et al. (4) demonstrated that heat was the only factor effective in killing Streptococcus faecalis and Saccharomyces cerevisiae cultures by enclosing he
test organisms in a Liebig condenser and varying the temperature during exposure from 25 to 55°C.
A practical application for the irradiation effect of microwave ovens on bacteria was suggested by Bush (1). Qualitative experiments done in his laboratory indicated that it was possible to use microwave ovens to decontaminate media used in clinical microbiology. Based on the above data, a quantitative study was undertaken in this laboratory to determine the effect of timed microwave irradiation on commonly encountered bacterial pathogens and to evaluate its possible utilization in a clinical situation.

DESINFECTING SEEDS

4.5. DESINFETANTES E ESTERILIZAÇÃO DO MEIO DE CULTURA

Os desinfestantes mais comumente usados em cultura de tecidos de plantas estão apresentados na tabela 2.

Tabela 2: Desinfestantes mais comumente usados em cultura de tecidos de plantas. (Extraído do Catálogo da Sigma).

Desinfestante	Concentração(%)	Exposição (min.)
Hipoclorito de Cálcio	9-10	5-30
Hipoclorito de Sódio	0,5-5,0	5-30
Água Oxigenada	3-12	5- 15
Álcool etílico	70-95	5- 15
Nitrato de prata	1	5-30
Cloreto de mercúrio	0,1-1,0	2-10

Cutting Propagation I

Microwave sterilization of Media

Would you Sterilise Growth Media With A Microwave?

May 06, 2008 by Nick in Tech Tips

We have had a rush on time and money saving techniques on Bitesize Bio in the last few weeks. Ways to re-cycle electroporation cuvettes, reduce gel buffer costs, do fast restriction digests and re-cycle midiprep columns have all been suggested.

In this article I’ll add the possibility of using a microwave to sterilize or decontaminate growth media. From the outset I’d like to say that I am not too sure about this, but I’ll make the case and you can tell me what you think.

Normally, growth medium is sterilized or decontaminated using an autoclave. Autoclaves are generally expensive, energy-hungry beasts that (in my experience) break down a lot so I would be very happy to use them less if I could.

Decontamination using microwaves.

The case for using microwave ovens for decontamination of cultures or materials was made back in 1977 by Latimer and Matsen. They showed that 1-5 minutes in a conventional microwave was sufficient to decontaminate 5mL cultures or petri dishes of common clinical pathogens includingE. coli, S. aureus and K. pneumoniae. B. subtilis spores proved a bit more subborn, requiring more than 10 minutes of microwaves to wipe them out.

Border and Rice-Spearman backed this up with a 1999 study that showed materials contaminated with various bacteria and yeast strains were completely decontaminated by one minute in the microwave (I guess their microwave was better). And in 2006, Silva et al, investigating the decontamination of dentures, showed that 6 minutes in the microwave sterilised S. aureus and C. albicans but only partially disinfected P. aeruginosa and B. subtilis.

Sterilisation using microwaves

A 2001 Biotechniques paper by Weiss and Galande showed that LB plates made from microwave-sterilised LB-agar were apparently sterile (control plates were no detectably contaminated by microorganisms), had a similar shelf-life to autoclaved plates and supported bacterial growth as normal. The plates were prepared from dry powders dissolved in distilled water and aliquoted into 50mL tubes.

This is a very fast way to make plates and has the added advantage that the antibiotics can be added in from the start as they are not destroyed by microwaves. Invitrogen have a product that takes advantage of this. ImMedia is LB medium provided as sachets of dried, weighed power containing all of the required media components (including antibiotics). It is designed so that you can just add the sachet contents to water, microwave and your media is ready. But Weiss and Galande’s method is just as good and much cheaper.

My view

My take-home from this is that microwaves are are reasonably good at decontamination but more stubborn microorganisms (e.g. the spore-forming B subtilis) are not effectively disinfected. So the method does not sound too reliable to me. Also, filling the lab with smelly fumes from contaminated stocks does not seem to be a good idea. For easy liquid culture decontamination I think I will stick with Virkon, and for solid media, autoclaving seems to be the only good option.

The microwave media prep method is certainly interesting. Weiss and Galande’s results seem to be pretty robust and I would consider this method for an emergency media prep – if I need to start an E. coli culture last thing at night and there’s no sterile media available. Although the decontamination results show that microwaves don’t kill everything, E. coli grows so quickly that for routine purposes, a low level of contamination by slower growing organisms can be tolerated.

But I would not use this method for anything other than routine cultures and certainly not for slow growing organisms. Maybe that’s just me being a typical scientist, reluctant to take on new methods as Liam suggested. The microwave method is also limited by the fact that only small volumes (50ml) can be sterilised so it is never going to replace the autoclave for batch media production.

That’s my view – what’s yours?

SOURCE: This article has been copied and pasted from

Http:\\http://bitesizebio.com/articles/would-you-sterilise-growth-media-with-a-microwave/ May 4, 2012 at 14:52 hours.

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