Research On Microbial Growth Detection Based On Spectral Technique

Microorganisms are widely distributed in the earth’s surface and various extreme environments. There is a large number of dependency relation with microbes and other organisms. In the natural world, microorganisms not only participate in the cycle of C, N, S and other elements, but also participate in agriculture to make fertilizer, to prevent bacteria and catalyze growth by bacteria, in the industrial to manufacture leather, to treat waste water, to degrade organic phosphorus and toxic substances.And microorganisms play a important role in engineering and enzyme engineering. However, a few harmful microorganisms are also harm to human life, mainly reflected in water pollution of intestinal pathogenic bacteria, the source of non intestinal microbial pollution, microbial invasion in the process of food harvesting, transportation and storage, intervening treatment of clinical medicine. Studies of microbial growth in different environments on one hand have contributed to the understanding of microbial properties, so as to make full use of micro-organisms beneficial role for the benefit of mankind, and on the other hand ultra fastly diagnosis harmful microbes and eliminate the harm brought by the harmful microorganisms to humans.At present, the detection method of microbial growth is mainly divided into two categories:invasive measurement and non-invasive measurement. In the early stage, it mainly focused on the intrusive measurement, including the dry weight method, the volume measurement method, the mycelium length measurement method, the microbial count method, the physiological index method and so on. But because these operators not only need to learn the skills of using microscope, gradient dilution of bacteria, bacteria liquid coating, centrifugation. acid-base titration, preparation solution and other professional technology, but also accept the heavy workload, time-consuming operation, acquisition of the sampling points, invasive operation caused by bacteria interference, the reduced culture medium and other factors, the test result is not accurate and ineffective.Microbial growth was accompanied by a series of parallel physiological indicators which can be applied for rapid growth. These indicators mainly includes the index of P, DNA, RNA, ATP, NAM, acid production, gas production and carbon dioxide (labeled glucose as substrate), oxygen consumption, viscosity, transparency and heat production. These phenomena constitute to the basic principles of the current non intrusive microbial measurement methods. In recent years, it has been suggested that the microbial sensor for the analysis of these biological indicators has been put forward by the researchers. Retrieving the changes of these biomarkers to obtain the growth state of the microorganism become the mainstream of seeking non-invasive, rapid, accurate, simple and automated microbial growth detection method.Carbon dioxide as metabolites of living microorganisms, the amount of carbon dioxide varying with time reflects the state of bacteria growth. At present, the detection method based on carbon dioxide has been applied to the measurement of microbial growth curve. Tunable diode laser spectroscopy (TDLAS) as a response time, high sensitivity, strong selectivity, high resolution, simple structure, non intrusive type of trace gas detection technology has been successfully applied for air monitoring, industrial emissions. Wavelength modulation spectrum technique as a tunable semiconductor spectrum technology, which suppress background noise signal by modulating laser wavelength, can raise detection sensitivity about two orders of magnitude and detect lower gas concentration.In this paper, we studied a growth curve measurement method of microbial growth in a closed space within the limited nutrient, and obtained a non intrusive, response time, high sensitivity and high resolution advantage of microbial curve measurement method. By taking this approach, we can obtain the relationship between microbial growth parameters of different culture conditions and environmental factors by fitting the measured curves. At the same time, we propose a kind of wavelength modulation spectroscopy measurement of pressure compensation scheme, overcome the measurement error caused by pressure variation in measurement process.Finally, we have applied this research method in blood cultures to detect bacteria. Compared with existing instruments, the positive alarm results of anaerobic culture bottle agree as well as our instrument. And the positive alarm results of aerobic, facultative anaerobic culture bottle have only one error and no false negative results, at the same time, we have confirmed a false positive results obtained by existing instruments. In all, this method is well measured. The results will further promote the application of TDLAS technology in microbial growth detection and pave the way for the future research. Finally, we summary the full text, and put forward the prospects of future research.