Abstract: Highly pure butanol can be produced by a method for producing butanol, the method comprising: Step A, wherein a butanol-containing solution is filtered through a nanofiltration membrane and a butanol-containing solution is recovered from the permeate side; Step B, wherein the butanol-containing solution obtained in Step A is passed through a reverse osmosis membrane and thereby concentrated to cause two-phase separation into a butanol phase and an aqueous phase; and Step C, wherein butanol is recovered from the butanol phase obtained in Step B.

Abstract: A method of producing lactic acid by separating lactic acid produced in a culture solution by microbial fermentation, comprising: a step (A) of filtering the culture solution through a nano-filtration membrane; and a step (B) of distilling a lactic-acid-containing solution produced in step (A) under a pressure of 1 Pa to atmospheric pressure at a temperature of 25 to 200° C. to recover lactic acid.

Abstract: A method for producing a diamine includes purifying a diamine from an aqueous solution containing a diamine salt by adding an alkaline substance to the aqueous solution and then filtering the resulting solution by allowing the solution to pass through a nanofiltration membrane to remove the salt, thereby obtaining an aqueous diamine solution.

Abstract: A method for producing a diol or triol, which has a step of removing impurities contained in a diol- or triol-containing solution, is provided. In the method, a diol- or triol-containing solution is filtered through a nanofiltration membrane having a polyamide-containing functional layer. The diol- or triol-containing solution is then collected from the permeate flow of the nanofiltration membrane.

Abstract: A method of producing butanol, which has a step of removing impurities contained in a butanol-containing solution, is provided. In the method, a butanol-containing solution is filtered through a nanofiltration membrane. Then the butanol-containing solution is collected from the permeate flow of the nanofiltration membrane.

Abstract: A sugar liquid containing only very small amounts of fermentation-inhibiting substances is produced by a method for producing a sugar liquid using a cellulose-containing biomass as a raw material, the method including: (1) a step of hydrolyzing a cellulose-containing biomass to produce an aqueous sugar solution; and (2) a step of filtering the obtained aqueous sugar solution through a nanofiltration membrane and/or reverse osmosis membrane to collect a purified sugar liquid from the feed side, while removing fermentation-inhibiting substances from the permeate side.

Abstract: A method for producing a diamine includes purifying a diamine from an aqueous solution containing a diamine salt by adding an alkaline substance to the aqueous solution and then filtering the resulting solution by allowing the solution to pass through a nanofiltration membrane to remove the salt, thereby obtaining an aqueous diamine solution.

Abstract: Disclosed is a lactic acid production method by separating lactic acid produced in a culture solution by means of the fermentation culture of a microorganism. Specifically disclosed is a lactic acid production method, which comprises: a step (A) of filtering the culture solution through a nano-filtration membrane; and a step (B) of distilling a lactic-acid-containing solution produced in the step (A) under a pressure ranging from 1 Pa to the atmospheric pressure (inclusive) at a temperature ranging from 25 to 200° C. (inclusive) to collect lactic acid. The method can effectively remove an inorganic salt dissolved in a fermentation culture solution or contained in the fermentation culture solution in the form of a poorly soluble solid material by a simple manipulation, enables to prevent the racemization or oligomerization of lactic acid during the process of producing lactic acid, and therefore can produce lactic acid in a high yield.