Preparation of Komagataeibacter xylinus Inoculum for Bacterial Cellulose Biosynthesis Using Magnetically Assisted External-Loop Airlift Bioreactor.

Anna Żywicka,Rafał Rakoczy,Adam Junka,Radosław Drozd,Maciej Konopacki,Daria Ciecholewska-Juśko,Marian Kordas,Paweł Migdał,Karol Fijałkowski

doi:10.3390/polym13223950

Abstract

The aim of this study was to demonstrate the applicability of a novel magnetically assisted external-loop airlift bioreactor (EL-ALB), equipped with rotating magnetic field (RMF) generators for the preparation of Komagataeibacter xylinus inoculum during three-cycle repeated fed-batch cultures, further used for bacterial cellulose (BC) production. The fermentation carried out in the RMF-assisted EL-ALB allowed to obtain an inoculum of more than 200× higher cellular density compared to classical methods of inoculum preparation. The inoculum obtained in the RMF-assisted EL-ALB was characterized by a high and stable metabolic activity during repeated batch fermentation process. The application of the RMF-assisted EL-ALB for K. xylinus inoculum production did not induce the formation of cellulose-deficient mutants. It was also confirmed that the ability of K. xylinus to produce BC was at the same level (7.26 g/L of dry mass), regardless of inoculum age. Additionally, the BC obtained from the inoculum produced in the RMF-assisted EL-ALB was characterized by reproducible water-related properties, mechanical strength, nano-fibrillar structure and total crystallinity index. The lack of any negative impact of inoculum preparation method using RMF-assisted EL-ALB on BC properties is of paramount value for its future applications, including use as a biomaterial in tissue engineering, wound healing, and drug delivery, where especially BC liquid capacity, nanostructure, crystallinity, and mechanical properties play essential roles.

Highlights

Bacterial cellulose (BC) is a polysaccharide polymer synthesized by a variety of bacteria, including non-pathogenic Komagataeibacter genus
It was confirmed that exposure to the rotating magnetic field (RMF) caused a significant increase in growth of K. xylinus cells during first cycle as compared to the fermentation process carried out under the same conditions but without exposure to RMF (Figure 3a)
Second and third fermentation cycle were carried out until the number of K. xylinus cells reached the values from the first cycle, which was achieved after 36 h (Figure 4a)

Summary

Introduction

Bacterial cellulose (BC) is a polysaccharide polymer synthesized by a variety of bacteria, including non-pathogenic Komagataeibacter genus (formerly known as Gluconacetobacter). BC has attracted significant interest thanks to its unique physical and chemical properties Such characteristics as high tensile strength, extremely hydrophilic surface, unique nanostructure, excellent biodegradability, and biological affinity make BC a promising material in a broad spectrum of applications, including medicinal dressings and food production, to name just a few [1,2,3,4]. Inoculum preparation is a process in which dormant microbial cells are introduced from a stock culture to a favorable environment and grow to form a metabolically active microbial population. Such cells can be used for inoculation in the productive stage in a bioreactor [7]. The above statement concerns the production of BC, with the exception of a single scientific publication by Wang et al, there are presently no reports on the optimization of K. xylinus inoculum preparation or comparisons of inoculum preparation methods [14]

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Conclusion