Comparison of laser diffraction and image analysis for measurement of Streptomyces coelicolor cell clumps and pellets

Abstract

Morphology is important in industrial processes involving filamentous organisms because it affects the mixing and mass transfer and can be linked to productivity. Image analysis provides detailed information about the morphology but, in practice, it is often laborious including both collection of high quality images and image processing. Laser diffraction is rapid and fully automatic and provides a volume-weighted distribution of the particle sizes. However, it is based on a number of assumptions that do not always apply to samples. We have evaluated laser diffraction to measure cell clumps and pellets of Streptomyces coelicolor compare to image analysis. Samples, taken five times during fed-batch cultivation, were analyzed by image analysis and laser diffraction. The volume-weighted size distribution was calculated for each sample. Laser diffraction and image analysis yielded similar size distributions, i.e. unimodal or bimodal distributions. Both techniques produced similar estimations of the population means, whereas the estimates of the standard deviations were generally higher using laser diffraction compared to image analysis. Therefore, laser diffraction measurements are high quality and the technique may be useful when rapid measurements of filamentous cell clumps and pellets are required.

Princípios fundamentais dos lasers e suas aplicações

“…Ainda sobre o processo de detecção de micro-organismos, o uso da luz laser tem ganhado destaque nas análises de estrutura e mensuração de aglomerados celulares, como visto no trabalho de Ronnest e colaboradores 150 , que demonstra a importância da difração laser como instrumento de comparação com a análise de imagem de grupos celulares de Streptomyces coelicor.…”

The Taming of the Shrew - Controlling the Morphology of Filamentous Eukaryotic and Prokaryotic Microorganisms

“…The light-scattering properties are converted to a size distribution by applying mathematical models, namely the Fraunhofer approximation for particles larger than 50 µm and the Mie theory for all particles. However, these mathematical models assume that the measured particles are spherical, which might lead to inaccurate results depending on the aspect ratio and flow orientation of the clumps and pellets [225].…”

“…Rønnest et al [225] evaluated the feasibility of laser diffraction measurements for the characterisation of S. coelicolor pellets and clumps by comparing them to conventional image analysis results. It was found that laser diffraction resulted in similar particle size distributions to image analysis, whereas the standard deviations were generally higher, presumably because of discrepancies between the assumptions for the mathematical model and the biological sample and statistical artefacts based on the small number of particles analysed by image analysis.…”

Bis‐arylidene Oxindoles as Anti‐Breast‐Cancer Agents Acting via the Estrogen Receptor

“…This makes the requirements for analysis methods to document the change of morphology rather demanding. A least, pelleted biomass is spherical and almost non‐transparent which could enable the utilization of classic particle size analysis like laser diffraction [67] and focused beam reflectance [66]. For tracking biomass development, also for other organisms, different technologies like capacitance probes, multi‐wavelength spectroscopy, scanning di‐electric spectroscopy, turbidity measurement and, of course image analysis (semi‐ and automatic), are available [68–7068–70].…”