DRASTIC(Diffuse Reflectance Absorbance Spectroscopy Taking In Chemometrics): A novel, rapid, hyperspectral, FT-IR-based approach to screening for biocatalytic activity and metabolite overproduction

Diffuse-reflectance absorbance spectroscopy in the mid-infrared is a novel method of producing data with which to effect chemical imaging for the rapid screening of biological samples for metabolite overproduction. We have used mixtures of ampicillin and Escherichia coli, and Streptomyces citricolor producing aristeromycin and neplanocin A, as model systems. Deconvolution of the hyperspectral information provided by the raw diffuse reflectance-absorbance mid-infrared spectra may be achieved using a combination of principal components analysis (PCA) and supervised methods such as artificial neural networks (ANNs) and partial least squares regression (PLS). Whereas a univariate approach necessitates appropriate data selection to remove any interferences, the chemometrics/hyperspectral approach could be employed to permit filtering of undesired components either manually, or by taking the Fourier transform of the spectral information (in order to help isolate the signal from the baseline variation or noise) prior to applying linear multivariate regression techniques. Equivalent concentrations of ampicillin between 0.2mM and 13.5mM in an E. coli background could be quantified with good accuracy using this approach.