Optimization of Key Factors Affecting Hydrogen and Ethanol Production from Xylose by Thermoanaerobacterium calidifontis VCS1 Isolated from Vinasse Treatment Sludge

Purpose This research aimed at isolating and characterizing an ethanol and H 2 -producing strain from a thermophilic consortium, obtained from sludge from anaerobic reactors applied to sugarcane vinasse treatment, evaluating its fermentative activity and its main metabolites in optimal pH and substrate (xylose) ranges by means of Rotational Central Composite Design (RCCD). Methods An anaerobic strain 99% similar to Thermoanaerobacterium calidifontis (VCS1) was isolated from enriched Upflow Anaerobic Sludge Blanket (UASB) sludge, by using Anaerobic Mineral Medium (AMM) under 55 °C and pH 7.0. Its kinetics parameters were evaluated using xylose as the sole substrate, it was possible to establish the generation time ( Tg = 9.12 h) and the specific growth rate (μ = 0.076 h −1 ). Besides that, the statistical method of RCCD was efficiently applied in order to find the optimal xylose concentration (3.6 to 69.5 mmol L −1 ) and pH (5.9 to 8.1) ranges to H 2 and/or ethanol production. Results The H 2 production was 20.4% improved at pH 6.8 and 33.8 mmol xylose/L, while ethanol production was 82.1% improved at pH 7.0 and 36.6 mmol xylose L −1 . For the simultaneous production of H 2 and ethanol, the best conditions were pH 7.0 and 36.0 mmol xylose L −1 . Conclusion The cultivation and enrichment of T. calidifontis VCS1 to degrade xylose-containing wastes might enhance the production of by-products of biotechnological interest, such as H 2 and ethanol. The results reported may subside future studies regarding up-scaling xylose biodegradation processes, by using the optimal range described. Graphical Abstract