BACKGROUND: Acetic acid is an important reagent and precursor in chemical and material industries. It is largely manufactured from fossil resources, but with increasing environmental concerns and uncertain petroleum availability, producing organic acids from renewable biomass has become a priority. Several researchers have demonstrated acetic acid production from model compounds, food products or a minor portion of lignocellulosic biomass but the simultaneous fermentation of all biomass-derived products has not been reported yet. This work demonstrates the unique capabilities of Clostridium thermoaceticum and Clostridium thermocellum in co-culture to convert most products obtained from hot-compressed water treatment of Japanese cedar into acetic acid.RESULTS: Under an optimal pH found to be 6.5, most cello-oligosaccharides and xylo-oligosaccharides as well as the majority of monosaccharides were completely consumed after 40 h, while the lignin-derived products, organic acids, decomposed and dehydrated compounds required 72 h to be fermented. Overall, it was found that most of the water-soluble lignocellulosic hydrolyzates were successfully transformed into acetic acid, leading to a high carbon conversion efficiency of 84.9%. CONCLUSION: Biomass-derived compounds from hot-compressed water treatment were efficiently converted to acetic acid, a valuable intermediate for further biotechnological production of chemicals and materials to substitute fossil-derived ones.