Abstract: The present technology relates to commercial-scale methods for purifying botulinum toxin compositions obtained from cell cultures. Purification methods according to the present disclosure are based on a series of filtration and chromatographic separation steps that produce a high-purity botulinum toxin composition, which comprises botulinum toxin protein molecules (˜150 kDa) in solution, which is free, essentially free, or substantially free of botulinum toxin complexes and animal products, and without precipitating or lyophilizing botulinum toxin protein molecules. The purification method according to the present disclosure uses no precipitation, lyophilization, or centrifugation steps, permitting production of highly pure, highly active, free botulinum toxin protein molecules (˜150 kDa) in solution, without the need for reconstitution by the end user.