A new screening method for recombinant Saccharomyces cerevisiae strains based on their xylose fermentation ability measured by near infrared spectroscopy
Fuel ethanol produced from lignocellulose by the yeast Saccharomyces cerevisiae becomes an increasingly important alternative to fossil fuels. Selection of S. cerevisiae strains, which can effectively produce ethanol from xylose is crucial to improve the fuel yield from lignocellulose. In the present study, a universal calibration system was developed by the combination of time series, fermentation near infrared (NIR) spectral data analysis and reference high-performance analysis of a single yeast strain which enabled the evaluation of the ethanol production ability of a wide variety of xylose-fermenting yeast strains. Subtraction of xylose and ethanol concentrations at 0 h for each clone, as well as the respective spectra, reduced subtle errors of the fermentation components naturally occurring in multiple experiments to clearly visualize the difference of fermentation ability between strains. Also, NIR spectra showed specific peaks in difference spectra calculated from the subtraction treatment. A robust univariate linear regression model led to high prediction accuracy of xylose consumption (R2 > 0.99) and ethanol production (R2 > 0.98) for a wide variety of yeast strains when using only the distinct spectral pattern of a single-strain. Here, a novel method for screening of high-performing yeast strains has been developed requiring only a simple single-strain calibration model. The advantages of NIR spectroscopy such as rapid and convenient experimental preparation using electromagnetic waves in the region, which provide deep penetration into an aqueous sample, are successfully exploited in the proposed screening method.