Dear colleagues:
I am interested in lactose determination and following during a fermentation process on cheese whey. I would like to perform the determination by the sequential treatment of samples with
1) beta-galactosidase, in order to hydrolyze lactose in glucose and galactose, and
2) GOD-POD system (enzymatic colorimetric assay), in order to quantify the glucose released in the previous step. This is the method used, for example, by Aktaş et al. (2006).
I would like to confirm that, as I am supposing, galactose is not interfering with glucose in the GOD-catalyzed step. I could only found the following material clearly affirming that: http://www.aemps.gob.es/informa/notasInformativas/medicamentosUsoHumano/seguridad/2010/NI_2010_009_PS_2010_05_H_glucosa.htm, but as I could find commercial kits including GOD-POD for lactose determination as in https://secure.megazyme.com/Lactose-Sucrose-D-Glucose-Assay-Kit, it seems feasible.
I would be pleased if anyone can share its own opinion, knowledge or additional material with respect to the question.
I would also like to know if lactose hydrolysis catalyzed by commercial beta-galactosidase is in general a quantitative conversion.
Bibliography:
Aktaş, N., Boyacı, İ. H., Mutlu, M., & Tanyolaç, A. (2006). Optimization of lactose utilization in deproteinated whey by Kluyveromyces marxianus using response surface methodology (RSM). Bioresource technology, 97(18), 2252-2259.
Greetings
Roberto
Additional Information:
Please see the files listed in this link.
In the International Dairy Federation Method (79B:1991) for the measurement of lactose in “dried milk, dried ice-mixes & processed cheese”, details are given for deproteinisation of samples, hydrolysis of lactose with β- galactosidase and measurement of either released D-galactose or D-glucose.
Enzymatic methods for the measurement of lactose are well known and are generally based on the hydrolysis of lactose to D-galactose and D-glucose with β-galactosidase, followed by determination of either D-galactose or Dglucose.The measurement of lactose as D-galactose liberated is more generally reliable than measurement as D-glucose liberated because preparations generally contain more free D-glucose than free D-galactose.
http://www.microbioland.gr/eshop/pdf-upload/EZS784.pdf
https://secure.megazyme.com/files/Booklet/K-LACGAR_DATA.pdf
Dear Laxmana:
Thnak you very mucho for your answer. I undestood that choosing between measuring released D-galactose or D-glucose is not a problem of interference, because enzymes used are very specific. If free D-glucose that may be present in the samples before treatment with beta-galactsidase, you can measure the level of D-glucose before the addition of the enzyme to not overestimate levels of lactose
Dear dr. Ceruti
The attached article will be helpful for you.
with regards
Dear Abdel, thank you for your answer, I've been looking up the article and it will be useful to me, as the authors cuantify lactose by cuantifying D-glucose released, and also as they show how do they manage enzyme quantities added
- Badges
- Science topic
- Similar topics
- Biological Science
- Biochemistry
- Enzymology
- Enzymes