Research On The Method Of Near-infrared Detection Of E.coli

Near-Infrared spectroscopy detection technique is one of the fast developing technology,which is nondestructive, fast, efficient, converient, and environmentally friendly. The thesis explores the action mechanisms of near-infrared spectroscopy in the detection of pathogenic bacterias, analyses the spectral pretreatment meghods of near-infrared spectral analysis technology, taking E.coli and LM as the research object which is in the logarithmic growth phase, using projection discriminant analysis based on PCA to identification of the pathogen for a study to get the expected result.1.Carried out a research into logarithmic growth phase of E.coli, taking the use of photoelectric turbidimetry and the plate colony count method. In this study, the Growth curves of E.coli is compared by two methods, from which we can see the growth trend of E.coli so as to determinate the E.coli logarithmic growth phase. At last, 14h was selected to next test.2.Taked a study on the cell disruption parameter of E.coli , based on the single-factor test and orthogonal experiment. It researchs the disruption parameter of E.coli, looking the rate of cell fragmentation efficiency as an indicator. In the end of this study, the best parameter combination broken was as follows: the power output was 400W, the time required for each step was 5s, and the total time was 50min.3.Inspected four different mothods of vector normalization, multi-dimensional scattering, first-order derivative, and a derivative of vector normalization method, according to the different concentration gradient of near infrared spectra of E.coli cell wall and cytoplasmic . The results showed that first-order derivative method and first-order derivative of vector normalization method of spectral pretreatment effect was not ideal, and using vector normalization method and multivariate calibration method of spectral pretreatment can receive the satisfactory results.4.A study about the near-infrared on E.coli cell wall and cytoplasmic effects had been carried out, using the projection discriminant analysis which is based on principal component analysis. The results show that the bacteria concentration on near-infrared absorption is not a concentration ratios, but the cell wall and cytoplasmic near-infrared absorbing is considerably different. In other words, the near-infrared absorption spectrometry can be used to distinguish between E.coli and LM.5.Both the cell wall and the cytoplasm of near-infrared spectra can be used to distinguish E.coli from LM, through the analysis of projection discriminant which is based on the principal component analysia. In addition, the near-infrared spectroscopy of cell wall can distinguish between E.coli and LM more accurately.