Real-time sensing of acetaldehyde in the headspace of yeast cultures using mid-infrared laser absorption spectroscopy
摘要
Mid-infrared laser absorption spectroscopy measurements of acetaldehyde in the headspace of yeast cultures are reported. An interband cascade laser (ICL) with single-mode tuning between 1770.19 and 1770.35 cm−1 was used to excite specific rotational-vibrational modes of motion in the R-branch of the carbonyl stretch absorption band for acetaldehyde. Real-time acetaldehyde measurements of seven different yeast cell cultures showed the effects of sucrose feeding, malted barley extract feeding, and anaerobic culturing. Acetaldehyde concentrations were as high as 62.8 ppm, observed 3 h after feeding yeast a 0.24 M sucrose solution. Typical concentration trends involved a peak in acetaldehyde concentration within 10 h of a feeding before leveling off to a lower concentration. These observations, along with the dramatic reduction in acetaldehyde observed with anaerobic culturing, are consistent with acetaldehyde production from pyruvate during a glucose consumption phase followed by acetaldehyde production from ethanol with enzymatic assistance from alcohol dehydrogenase (ADH) and the oxidized form of nicotinamide adenine dinucleotide (NAD+).