Acetone Bio-Sniffer (Gas-Phase Biosensor) for Monitoring of Human Volatile Using Enzymatic Reaction of Secondary Alcohol Dehydrogenase

We developed a highly sensitive acetone bio-sniffer (gas-phase biosensor) based on an enzyme reductive reaction to monitor breath acetone concentration. The acetone bio-sniffer device was constructed by attaching a flow-cell with nicotinamide adenine dinucleotide (NADH)-dependent secondary alcohol dehydrogenase (S-ADH) immobilized membrane onto a fiber-optic NADH measurement system. This system utilizes an ultraviolet light emitting diode as an excitation light source. Acetone vapor was measured as the fluorescence of NADH consumption by the enzymatic reaction of S-ADH. A phosphate buffer that contained oxidized NADH was circulated into the flow-cell to rinse the products and the excessive substrates from the optode; thus, the bio-sniffer enables the real-time monitoring of acetone vapor concentration. A photomultiplier tube detects the change in the fluorescence emitted from NADH. The relationship between the fluorescence intensity and acetone concentration was identified to be from 20 ppb to 5300 ppb. This encompasses the range of concentration of acetone vapor found in the breath of healthy people and of those suffering from disorders of carbohydrate metabolism. Then, the acetone bio-sniffer was used to monitor the exhaled breath acetone concentration change before and after a meal. When the sensing region was exposed to exhaled breath, the fluorescence intensity decreased and reached saturation immediately. Then, it returned to the initial state upon cessation of the exhaled breath flow. We anticipate its future use as a non-invasive analytical tool for the assessment of lipid metabolism in exercise, fasting and diabetes mellitus.

New species within Candida parapsilosis and Candida glabrata

Introduction: Candida parapsilosis and Candida glabrata are another yeasts that form complexes of crypospecies. Although these species have been described more than a decade ago, knowledge about them is still limited. The reason for this is the large phenotypic similarity that unables them from being differentiated by classical diagnostic methods. The aim of the study was to identify species of clinical strains within C. glabrata and C. parapsilosis complexes. Material and methods: Standard PCR-RFLP of the secondary alcohol dehydrogenase gene (SADH) with BanI restriction enzyme served to determine species affiliation within the C. parapsilosis complex. The internal transcribed spacer was used to confirm the identification of C. glabrata sensu stricto. The D1/D2 domain of the 26S rDNA gene was sequenced in order to identify C. nivariensis and C. bracarensis strains. Results: As a result of the molecular analysis, 24 Candida nivariensis isolates and 4 C. metapsilosis strains and 9 C. orthopsilosis strains were detected. Conclusions: Prevalence of new cryptic species was relatively low.

Cofactor specificity engineering of a long-chain secondary alcohol dehydrogenase from Micrococcus luteus for redox-neutral biotransformation of fatty acids

Structure-based cofactor specificity engineering of an alcohol dehydrogenase (mLSADH) enables a redox-neutral biotransformation of C18 fatty acids into C9 fatty acids.