The acid test: 21st century pH meter

Mar 28, 2012

Modern methods for mass production of biological agents and fine chemicals require precise control of pH. However within these systems it is not always possible to use traditional methods for measuring acidity and alkalinity. Biomed Central's open access journal BMC Biotechnology describes a new and user friendly method for measuring pH, which uses luminescent dual life-time referencing (DLR), to provide real-time characteristics of enzyme reactions.

Industrial methods for manufacturing compounds often requires the use of an enzyme (bio-catalyst). In order for the enzyme to be recovered and re-used at the end of the process they are usually attached to a carrier such as and then kept in suspension by continuous mixing of the reaction. Under these conditions, although the pH of the bulk liquid can be controlled it is difficult to accurately measure what is happening at the level of the enzyme. This is especially important for reactions which involve changes in proton concentrations.

A team from Graz University of Technology, Austria, have developed a luminescent method for measuring pH in enzyme reactions based on DLR. It combines a luminescent pH indicator and a reference standard which are excited at the same wavelength. Both indicator and standard also emit at similar wavelengths (different to the excitation ). The phase shift in the ratio of the two intensities alters with pH because there is difference in the time it takes for the indicator to decay.

The team led by Bernd Nidetzky tested the DLR-based pH meter on the reaction catalyzed by cephalosporin C amidase. This enzyme hydrolyses cephalosporin C, but the reaction results in the formation of a proton which can alter local pH relative to the surrounding liquid. Using the new pH meter the researchers were able to measure that the pH of the reaction initially dropped and then steadily rose as the substrate (cephalosporin C) was used up.

Prof Nidetzky explained, "This new method is self referencing and is easy to use because it only requires a single photodetector. It is not affected by optical interference in the same way as other luminescent pH meters and, because phase shift data are not affected by particle movement, this method is ideal for applications inside a stirred tank."

Explore further: Sieving for genes: Developmental regulation of important plant phloem components discovered

More information: Dual-lifetime referencing (DLR): a powerful method for on-line measurement of internal pH in carrier-bound immobilized biocatalysts Caterina Boniello, Torsten Mayr, Juan M Bolivar and Bernd Nidetzky BMC Biotechnology (in press)

add to favorites email to friend print save as pdf

Related Stories

Adjusting acidity with impunity

Dec 22, 2009

(PhysOrg.com) -- How do individual cells or proteins react to changing pH levels? Researchers at the MESA+ Institute for Nanotechnology at the University of Twente, The Netherlands, have developed a technique ...

Researchers use neutrons to spy on the elusive hydronium ion

Aug 08, 2011

A Los Alamos National Laboratory research team has harnessed neutrons to view for the first time the critical role that an elusive molecule plays in certain biological reactions. The effort could aid in treatment of peptic ...

Unlocking the function of enzymes

Nov 06, 2007

Fitting a key into a lock may seem like a simple task, but researchers at Texas A&M University are using a method that involves testing thousands of keys to unlock the functions of enzymes, and their findings could open the ...

New buffer resists pH change, even as temperature drops

Jan 14, 2008

Researchers at the University of Illinois have found a simple solution to a problem that has plagued scientists for decades: the tendency of chemical buffers used to maintain the pH of laboratory samples to lose their efficacy ...

Bacteria beat the heat

Aug 30, 2006

How do some microorganisms manage to exist and even thrive in surroundings ranging from Antarctica to boiling hot springs? A team of scientists from the Weizmann Institute's Plant Sciences Department, led by Prof. Avigdor ...

Recommended for you

Getting a jump on plant-fungal interactions

Jul 29, 2014

Fungal plant pathogens may need more flexible genomes in order to fully benefit from associating with their hosts. Transposable elements are commonly found with genes involved in symbioses.

User comments : 0