Biotechnological Conversion of Grape Pomace to Poly(3-hydroxybutyrate) by Moderately Thermophilic Bacterium <i>Tepidimonas taiwanensis</i>

Polyhydroxyalkanoates (PHA) are microbial polyesters that have recently come to the forefront of interest due to their biodegradability and production from renewable sources. A potential increase in competitiveness of PHA production process comes with a combination of the use of thermophilic bacteria with the mutual use of waste substrates. In this work, the thermophilic bacterium <i>Tepidimonas taiwanensis</i> LMG 22826 was identified as a promising PHA producer. The ability to produce PHA in <i>T. taiwanensis</i> was studied both on genotype and phenotype levels. The gene encoding the Class I PHA synthase, a crucial enzyme in PHA synthesis, was detected both by genome database search and by PCR. The microbial culture of <i>T. taiwanensis</i> was capable of efficient utilization of glucose and fructose. When cultivated on glucose as the only carbon source at 50 °C, the PHA titers reached up to 3.55 g/L, and PHA content in cell dry mass was 65%. The preference of fructose and glucose opens the possibility to employ <i>T. taiwanensis</i> for PHA production on various food wastes rich in these abundant sugars. In this work, PHA production on grape pomace extracts was successfully tested.