Production of L(+)-Lactic Acid from Mixed Acid and Alkali Hydrolysate of Brown Seaweed

The species of brown seaweeds, Laminaria japonica is commercially cultivated in Japan. Mannitol and uronic acid were the main component of mono sugar produced from the saccharification of L. japonica which hydrolysed with H2SO4 or NH4OH. The mannitol concentration of L. japonica (5 w/v %) hydrolysate using 0.5 v/v % H2SO4 or 1 v/v % NH4OH were 15.84 g/L and 13.87 g/L, respectively. Hydrolysates from both acid and alkali hydrolysis were mixed together for neutralization as well as to obtain higher mannitol concentration of 15.18 g/L. Among the mono sugar in the hydrolysate, Mannitol was the main substrate for the lactic acid fermentation by Lactobacillus rhamnosus. L(+)-Lactic acid with 97.9% of optical purity was successfully produced at the yield of 14.42 g/L (Yp/s = 94.99%).