Fermentation production of lactic acid directly from starch was studied in a membrane recycle bioreactor (MRB) using Lactobacillus amylovorus. With 50 g litre-1 liquefied starch as feed, essentially complete con version to lactic acid was obtained up to a dilution rate of 0.2 h-1; maximum productivity of 25 g litre-1 h was obtained at 0.5 h-1. A higher starch concentration in the feed caused lower conversions, resulting in rapid accumulation of unconverted starch in the fermenter. The MRB was operated continuously for 10 days without significant problems. Media components were responsible for fouling the membrane module.