Polylactic acid (PLA) is synthesized by direct polycondensation without catalyst (NC-DP) method using a lactic acid (HLa) solution which had been refined by concentration, esterification and hydrolysis of fermented broth from fresh cassava roots (FCR). Higher polymerization rates and earlier thermal degradation had been observed, compared with those from a pure lactic acid solution. It is due to residual impurities in refining process, such as butanol (BuOH) and butyl lactate (BuLa), which act as an external catalyst. Additionally, it has been found that thermal degradation of PLA containing these impurities occurs via random scission with vinyl end groups, in regard to specific scission for PLA from a pure HLa solution.