Chelatococcus thermostellatus sp. nov., a new thermophile for bioplastic synthesis: comparative phylogenetic and physiological study

Mohammad H A Ibrahim,Mohammad H A Ibrahim,Liesbeth Lebbe,Alexander Steinbüchel,Alexander Steinbüchel,Anne Willems

doi:10.1186/s13568-016-0209-9

Abstract

The poly(3-hydroxybutyrate), PHB, accumulating thermophilic strain MW9T, isolated from an aerobic organic waste treatment plant, was characterized by detailed physiological and phylogenetic studies. The strain is a Gram-stain-negative, rod shaped, non-spore forming member of Alphaproteobacteria. It shows optimum growth at 50 °C. Based on 16S rRNA gene sequence similarity, the strain together with five very similar isolates, was affiliated to the genus Chelatococcus (Ibrahim et al. in J Appl Microbiol 109:1579–1590, 2010). Rep-PCR genomic fingerprints and partial dnaK gene sequence also revealed that these isolates are very similar, but differ from other Chelatococcus type strains. The major fatty acids were similar to those of other strains of the genus Chelatococcus. DNA–DNA hybridization of strain MW9T with Chelatococcus species type strains revealed 11.0–47.7 % relatedness. G+C content of DNA was 67.1 mol%, which is comparable with the other strains of Chelatococcus species. The physiological and phenotypic characteristics of the new strain MW9T are sufficient to differentiate it from previously described species in the genus Chelatococcus. Strain MW9T is considered to represent a novel species of the genus Chelatococcus, for which the name Chelatococcus thermostellatus is proposed. The type strain is MW9T (=LMG 27009T = DSM 28244T). Compared to known Chelatococcus strains, strain MW9T could be a potent candidate for bioplastic production at elevated temperature.

Highlights

Increased global demands for alternative energy and biodegradable materials have stimulated many studies for the utilization of renewable resources via microbial fermentation (Chiellini and Corti 2012)
The isolates grew optimally at 50 °C and accumulate high content of PHB (Ibrahim et al 2010), whereas the other type strains of genus Chelatococcus did not grow at the temperature being investigated in this study (50 °C)
PHA accumulation A detailed investigation of PHA synthesis by the strains C. daeguensis LMG 25471T and C. sambhunathii LMG 26063T was conducted in the present study

Summary

Introduction

Increased global demands for alternative energy and biodegradable materials have stimulated many studies for the utilization of renewable resources via microbial fermentation (Chiellini and Corti 2012). Composting is a self-heating aerobic solid phase process for partial biodegradation and conversion of organic waste materials. A large variety of mesophilic, thermotolerant and thermophilic aerobic microorganisms have been reported to be predominant in composting at temperatures between 20 and 60 °C (De Bertoldi et al 1983). Temperature is revealed to be a major factor determining the type of microorganism, species diversity, and the rate of metabolic activities during composting. It has been reported that at temperature of 50–60 °C, thermophilic bacteria are very active composting organisms (Beffa et al 1995)

Methods

Results

Conclusion