Diversity of growth kinetic models for Rhizopus arrhizus

Abstract:

[Background] Strains of Rhizopus arrhizus vary in physiological and biochemical indicators, but relative genetic background is unclear, hindering their further applications in fermentation. [Objective] This study explored temperature-growth kinetic models among strains of R. arrhizus in order to lay a foundation for investigating population genetics and for screening materials potential in production. [Methods] R. arrhizus isolated from Asia and Europe were first identified by morphology and then by molecular phylogeny reconstructed with ITS and IGS rDNA. Finally, their temperature-growth kinetics was analyzed by directly measuring colonial diameters on medium plates. [Results] The temperature-growth kinetic models of R. arrhizus were diverse, and the curves significantly differ, with less relatedness to morphological and phylogenetic varieties. Lower restraining growth, optimum growth, higher restraining growth, and fatal temperatures were 4?9, 30?37, 40?49, and 40?52 °C, respectively. Strains XY00454 and XY00469 grew rapidly and adapted well to higher temperatures and therefore were potential for industrial production. [Conclusion] R. arrhizus is still evolving violently and diverging actively in morphology, molecular and physiology, while not developing any independent populations. It is feasible to screen fermentation potential isolates based on thermal adaptability.

Key words:Rhizopus oryzae, Physiological characteristics, Optimum growth temperature, Inhibiting growth temperature, Lethal temperature