Mixed fruit wastes (FW) are considered valuable organic wastes due to their polysaccharidic content. This study describes utilization of an effective acclimatized microbiome (AM) for enhanced conversion of FW into hydrogen and various value-added byproducts. Microbial acclimatization was used to accelerate two processes, hydrogenogenic acidogenesis and carboxylic chain elongation, which simultaneously produced hydrogen and C4-C7 carboxylates. AM showed 77 mL g(-1) VS of hydrogen yield with 31% higher specific hydrogen production potential (SHPP) compared to 55 mL g(-1) VS with an unacclimatized microbiome (UM). Production of carboxylates was also 19% higher in the AM. Taxonomic analysis of the microbiome revealed the microbial shift to Firmicutes as the most dominant phylum (99%). Clostridium, Hydrogenoanaerobacterium, Paraclostridium, Anaerosalibacter, Tissierella, and Tepidanaerobacter were preeminent genera in the AM, confirming their predominant role in dual processes. Thus, utilization of an AM enhanced the hydrogenogenic acidogenic fermentation of FW with simultaneous carboxylic chain elongation, yielding high-value products. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.