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: Sex chromosomes—why the Y genes matter

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)

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

Bacteria study could have agricultural impact

58 minutes ago

Wichita State University microbiology professor Mark Schneegurt and ornithology professor Chris Rogers have discovered that one of North America's most common migratory birds – the Dark-eyed Junco – carries ...

Sex chromosomes—why the Y genes matter

12 hours ago

Several genes have been lost from the Y chromosome in humans and other mammals, according to research published in the open access journal Genome Biology. The study shows that essential Y genes are rescue ...

Better mouse model enables colon cancer research

May 27, 2015

Every day, it seems, someone in some lab is "curing cancer." Well, it's easy to kill cancer cells in a lab, but in a human, it's a lot more complicated, which is why nearly all cancer drugs fail clinical ...

How to get high-quality RNA from chemically complex plants

May 26, 2015

Ask any molecular plant biologist about RNA extractions and you might just open up the floodgates to the woes of troubleshooting. RNA extraction is a notoriously tricky and sensitive lab procedure. New protocols out of the ...

Plant fertility—how hormones get around

May 26, 2015

Researchers at Tokyo Institute of Technology have identified a transporter protein at the heart of a number of plant processes associated with fertility and possibly aging.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.