Summary
Four methylotrophic bacteria, isolated at the Kuwait Institute for Scientific Research, were able to grow on methanol as the only carbon source at a maximum temperature of 44°C. An optimized medium composition was obtained through intensive chemostat studies varying both macro- and micro-element concentrations. Various batch and chemostat experiments were carried out at different pH, temperature, dilution rate and methanol concentrations. The results showed optimum pH around 6.8, at temperatures of 37 to 40°C, dilution rate 0.2–0.3 h−1 and methanol was found to be inhibitory at concentrations above 20 g l−1. The performance of all four bacteria under chemostat conditions was similar. Chemostat fermentation experiments using the optimized medium at 40°C, pH 6.8, dilution 0.2 h−1 and 10 g methanol/l in the feed gave a biomass yield coefficient of 0.42–0.44 g/g methanol, 78–79% crude protein content, 58–62% total amino acid content and 10–11.5% nucleic acid content. In conclusion all four methylotrophic strains has good potential for use in the production of single-cell protein.
Résumé
Quatre bactéries méthylotrophes, isolées à l'Institut pour la Recherche Scientifique du Kuweit, se sont révélées capables de croître sur méthanol comme seule source de carbone à une température maximum de 44°C. Des études intensives en chémostat de variation des concentrations tant en macro-qu'en micro-éléments, ont permis d'obtenir une composition optimum du milieu. Diverses expériences en milieu non renouvelé et en chémostat ont été effectuées à différents pH, températures, taux de dilution et concentration en méthanol. Les résultats ont montré un optimum de pH vers 6.8, de température entre 37 et 40°C, de taux de dilution de 0.2 à 0.3 h−1. Le méthanol s'est révélé inhibiteur aux concentrations supérieures à 20 g l−1. La performance des quatres bactéries dans les conditions du chémostat se sont révélées très semblables. Les expériences de fermentátion en chémostat, utilisant le milieu optimum à 40°C, pH 6.8, taux de dilution de 0.2 h−1 et à 10 g de méthanol par litre dans l'alimentation ont produit un coefficient de rendement en biomasse de 0.42 à 0.44 g de cellules par g de méthanol contenant de 78 à 79% de protéines, de 58 à 62% d'acides aminés totaux et de 10 à 11.5% d'acides nucléiques. En conclusion, les quatre bactéries méthylotrophes présentent une bonne potentialité pour être utilisées dans la production de protéine uni-cellulaire.
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Banat, I.M., Al-Awadhi, N. & Hamdan, I.Y. Physiological characteristics of four methylotrophic bacteria and their potential use in single-cell protein production. World J Microbiol Biotechnol 5, 149–159 (1989). https://doi.org/10.1007/BF01741838
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DOI: https://doi.org/10.1007/BF01741838