PhD Thesis

The Optimal Choice of a Generic Laser System for the Commercial Sterilisation of Micro-Organisms

PhD thesis

University of Wales, Swansea
July 2003

Abstract

This thesis describes the theory and practical application of controlled LASER radiation to denature micro-organisms on the surface of a given substrate in a commercial scale system. The described research system has been proven to achieve these aims tested on one specific bacterial example and one substrate.

The investigation evaluates the cell physiology of micro-organisms and the required physical and chemical parameters that are capable of denaturing them. A summary of the current state of sterilisation technologies with respect to their relative efficiencies and applications is presented, with specific attention being focused on the use of LASER light sources and their associated photo-thermal effects. The optimal choice of LASER wavelength is discussed together with its required spatial and temporal profiles to denature a broad range of micro-organisms.

The investigation centres on the use of continuous wave carbon dioxide lasers (with a wavelength of 10·6 µm) as the preferred choice to denature a variety of organisms, predominately Salmonella enteritidis, residing on the surface of chicken eggs destined for hatching. The initial trials showed that a kill rate of 99·988 % (3·9 log) could be achieved.

The research system has been developed in conjunction with ADAS Consulting Limited (ADAS), which was formerly a government body affiliated to the Ministry of Agriculture, Fisheries and Food.

[PDF : PhD thesis 3.9 MB]