Lipase-catalyzed esterification of lactic acid has thus far achieved only limited success due to high acidity and polarity of lactic acid: acid inactivation of enzymes, and immiscibility of lactic acid with hydrophobic organic solvents that are commonly used for non-aqueous enzyme reactions. Herein, we investigated enzymatic esterification of lactic acid with ethanol by using hydrophobic ethers and ketones as reaction media. Both of the solvents are miscible with lactic acid, and have the basicity to suppress the acid inactivation of enzymes, as well as polar solvents. Nevertheless, these solvents would be less harmful to enzymes rather than polar solvents because of their high hydrophobicity. Using the ethers and ketones, ethyl lactate was successfully synthesized enzymatically even at higher lactic acid concentrations, and the enzyme activity was effectively stabilized even in repeated batch-wise reactions (2.0 M lactic acid, 4 weeks). This effect of some ethers and ketone to stabilize the enzyme was significantly higher than that of polar solvents in the presence of polar alcohols, the other substrate. In addition, more various kinds of lipase could esterify 1.0 M lactic acid, in the hydrophobic ether and ketone rather than those in hydrophobic solvents, polar solvents, and a solvent-free system.
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Stress upsets belly's balance
Some people find exams and other stressful life experiences coincide with gastrointestinal problems. New research has shown that their stomachs may be churning for a reason.
Swinburne psychology lecturer Dr Simon Knowles along with his colleague biotechnology researcher Dr Enzo Palombo and PhD student Elizabeth Nelson have studied the effect of stress on gastrointestinal flora .
“This is the first study to show that perceived stress affects the levels of good bacteria in the intestine,” Knowles said. “A reduction in these good bacteria is associated with gastrointestinal infections .”
The group studied the effect of perceived stress on salivary cortisol concentrations and lactic acid bacteria activity on 23 healthy undergraduate students.
Saliva and faecal samples were collected from the students at the beginning of the academic semester to obtain a low stress baseline and again during the first week of exams. The students also completed a series of questionnaires about their perceived levels of stress, what they ate and gastrointestinal symptoms.
Predictably, the students rated their perceived levels of stress as being greater during the exam period compared to the beginning of the semester. The study also found a corresponding lowering of faecal lactic acid bacteria levels during the high stress condition.
“This is evidence that stress can have a pervasive impact on an individual’s physiological as well as their psychological well-being,” said study author Dr Simon Knowles.
“Despite extensive research on the influence of stress on immune functioning and well-being, little is known about the impact of stress on gastrointestinal microflora. This is the first human study to show a link between stress and gut flora.
“This is significant because a reduction in good gut flora may contribute to the onset of gastrointestinal problems.”
Knowles suggests that the findings of this study could lead to intervention using cognitive behaviour therapy to help people to deal with the effects of stress.
The findings are detailed in an article published in the February 2008 issue of Biological Psychology.
Swinburne University
Swinburne psychology lecturer Dr Simon Knowles along with his colleague biotechnology researcher Dr Enzo Palombo and PhD student Elizabeth Nelson have studied the effect of stress on gastrointestinal flora .
“This is the first study to show that perceived stress affects the levels of good bacteria in the intestine,” Knowles said. “A reduction in these good bacteria is associated with gastrointestinal infections .”
The group studied the effect of perceived stress on salivary cortisol concentrations and lactic acid bacteria activity on 23 healthy undergraduate students.
Saliva and faecal samples were collected from the students at the beginning of the academic semester to obtain a low stress baseline and again during the first week of exams. The students also completed a series of questionnaires about their perceived levels of stress, what they ate and gastrointestinal symptoms.
Predictably, the students rated their perceived levels of stress as being greater during the exam period compared to the beginning of the semester. The study also found a corresponding lowering of faecal lactic acid bacteria levels during the high stress condition.
“This is evidence that stress can have a pervasive impact on an individual’s physiological as well as their psychological well-being,” said study author Dr Simon Knowles.
“Despite extensive research on the influence of stress on immune functioning and well-being, little is known about the impact of stress on gastrointestinal microflora. This is the first human study to show a link between stress and gut flora.
“This is significant because a reduction in good gut flora may contribute to the onset of gastrointestinal problems.”
Knowles suggests that the findings of this study could lead to intervention using cognitive behaviour therapy to help people to deal with the effects of stress.
The findings are detailed in an article published in the February 2008 issue of Biological Psychology.
Swinburne University
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