The lack of a route to precursor 1,2,4-butanetriol that is amenable to large-scale synthesis has impeded substitution of 1,2,4-butanetriol trinitrate for nitroglycerin. To identify an alternative to the current commercial synthesis of racemic d,l-1,2,4-butanetriol involving NaBH4 reduction of esterified d,l-malic acid, microbial syntheses of d- and l-1,2,4-butanetriol have been established. These microbial syntheses rely on the creation of biosynthetic pathways that do not exist in nature. Oxidation of d-xylose by Pseudomonas fragi provides d-xylonic acid in 70% yield. Escherichia coli DH5alpha/pWN6.186A then catalyzes the conversion of d-xylonic acid into d-1,2,4-butanetriol in 25% yield. P. fragi is also used to oxidize l-arabinose to a mixture of l-arabino-1,4-lactone and l-arabinonic acid in 54% overall yield. After hydrolysis of the lactone, l-arabinonic acid is converted to l-1,2,4-butanetriol in 35% yield using E. coli BL21(DE3)/pWN6.222A. As a catalytic route to 1,2,4-butanetriol, microbial synthesis avoids the high H2 pressures and elevated temperatures required by catalytic hydrogenation of malic acid.