Pseudoxanthomonas taiwanensis and Pseudomonas thermotolerans : Novel Thermophilic Amylase Producers in Solid-State Fermentation

Amylases are key industrial enzymes, and thermostable variants are particularly valuable for robust bioprocessing. This study investigates amylase production via solid-state fermentation (SSF) using non-sterile potato peel as substrate, comparing the performance of the autochthonous microbial population with that of the inoculated fungus Thermomyces lanuginosus. Non-inoculated batch reactors reached maximum productivities of 3920 U g¹DM day¹, more than double of the inoculated ones (1823 U g¹DM day¹), highlighting the potential of native thermophiles. Sequential batch reactor (SBR) strategies were applied to promote microbial selection and monitor T. lanuginosus persistence over seven cycles. Although the inoculum initially increased overall microbial activity (sOUR), T. lanuginosus was not detected, and no sustained improvement in amylase productivity was observed. Three thermophilic amylase-producing strains were isolated: Bacillus coagulans, Pseudoxanthomonas taiwanensis, and Pseudomonas thermotolerans, the last two being newly reported amylase producers. These findings demonstrate that efficient, scalable amylase production can be achieved through non-sterile SSF relying on native microbial communities, supporting circular bioeconomy strategies and potentially reducing the need for external inoculation. Further work is needed to confirm the generalizability of these results and to better understand the interactions between inoculated and native strains.