PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 10445317

An improved method for screening alpha-acetolactate producing mutants.

C Monnet·S Haddad·G Corrieu
View original source ↗Export metadata ↓

Abstract

Alpha-Acetolactate-deficient Lactococcus lactis ssp. lactis biovar. diacelylactis are utilised in several industrial processes for producing diacetyl and alpha-acetolactate. They can be selected by screening after random mutagenesis. We improved a previously described screening method [Monnet, C., Schmitt, P., Diviès, C., 1997. Appl. Environ. Microbiol. 63, 793-795], which makes it possible to screen up to 1000 colonies per agar plate, whereas the previous method allowed to screen only 60 colonies per agar plate. The new screening method facilitates selection of alpha-acetolactate-deficient mutants.

Explore related subjects

FiltrationLactatesLactococcus lactisMutagenesisJournal ArticleResearch Support, Non-U.S. Gov't

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

C Monnet, S Haddad, G Corrieu. 1999. An improved method for screening alpha-acetolactate producing mutants.. https://doi.org/10.1016/s0167-7012(99)00063-9

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2007

Effects of filtration and pH perturbation on freshwater organic matter fluorescence.

Fluorescence of organic matter from six contrasting freshwaters was analysed after filtration (1.2 microm and 0.2 microm filter sizes) and pH perturbation (+/-2 pH units from ambient conditions). Two fluorophores were compared in detail: tryptophan-like fluorescence, whose filtration and pH characteristics are relatively poorly understood, and humic-like fluorescence, which is better characterised. Although there was some variability in both fluorophores, the tryptophan-like fluorescence showed the most significant decrease in fluorescence intensity between raw and 1.2 microm filter samples, and a much smaller decrease between 1.2 and 0.2 microm, demonstrating a significant source associated with particulate material as well as a significant <0.2 microm fraction. In contrast, humic-like fluorescence shows little change with filtration, suggesting that the majority of this fluorescence is associated with truly dissolved material. The pH perturbation experiments demonstrate that tryptophan-like fluorescence is less impacted by pH than with filter fraction. For humic-like fluorescence, pH effects are weak and are not as consistent as those reported in the literature for extracted humic substances. pH perturbation of the freshwaters shows a wide range of sample specific pH responses, significantly more variable than that observed in experiments using extracted humic substances and tryptophan standards, demonstrating the natural variability of freshwater dissolved organic matter.

Filtration↗
PubMed2006

[Approximation of collimator scatter factor Sc by a saturation model].

To more easily estimate accurate values of collimator scatter facor, S(c), we suggest a two-component saturation model that accounts for scatter from the primary collimator and flattening filter and from the collimator jaws. This model, which assumes an exponential distribution of scatter intensity, was tested by in-air measurements using a mini-phantom for 4 MV and 10 MV X-rays of a Clinac 2100 C/D linear accelerator. The results showed a good fit of this model to our measured data (R(2)>0.9993). When the measured value was divided into the primary collimator/flattening filter component and the collimator jaw component, as expected, the former component showed a rapid and full saturation curve with increased field size, while the latter showed an almost linearly increasing curve. Therefore, we think that this saturation model is useful for the estimation of S(c) and is applicable to monitor unit calculation for an asymmetric field.

Filtration↗
PubMed2006

Examination of beam profile measurement using an imaging plate by the light exposure fading method for quality assurance of external radiation therapy.

High-resolution film dosimetry has been used for several decades to check and to measure two-dimensional dose distributions. However, in recent years, the automatic processor has been replaced by the spread of computed radiography, or has been little used hospitals. In this study, we measured the off-center ratio (OCR) of the open field, after an irradiating radiation beam was delivered to the imaging plate (IP) under conditions in which the IP was exposed to a fixed amount of light with fading, and compared these data with the OCR measured by an ionization-chamber dosimeter, which is the standard method used for measuring radiation dose. Profile measurement using IP could be achieved by performing light fading, even at a range of more than 100 MU. Further, by using a metallic filter, we succeeded in demonstrating that the profile measurement of IP in an open irradiation field could approximate the values of those obtained by an ionization chamber dosimeter. This method can serve as a simple, easy-to-use method for evaluating the QA of dose distribution in radiation therapy.

Filtration↗