Prepurification of α-lactalbumin with ultrafiltration ceramic membranes from acid casein whey: Study of operating conditions

Abstract

A promising way to produce purified α-lactalbumin (α-LA) is to perform a two-step cascade. The first step of pre-purifying presented herein, consists of ultrafiltration (UF) fractionation of acid casein whey, aiming at increasing the purity of α-LA in the filtrate by total retention of bovine serum albumin and immunoglobulins with only a limited transmission of β-lactoglpbulin. The outcome of the present work is a guideline which includes the proper selection of ceramic UF membrane molecular mass cut-off (MMCO) (from 150 to 300 kg·mol-1), operating conditions (physico-chemistry, hydrodynamics) and operation mode for achieving satisfactory performance. Irreversible membrane fouling, mainly due to β-lactoblobulin (β-LG), the major protein of the feed solution, and physico-chemical characteristics of the whey protein sources (initial α-LA purity and concentration; heat denaturation of proteins) were shown as selection parameters of prime importance with regard to the target of the prepurification step. Whey protein concentrate in liquid form (PS 90) was to be preferred versus the same grade in powder form and the less concentrated liquid (PS 15). By processing that liquid PS 90, α-LA purity in the permeate was increased from around 0.25 in the initial feed to around 0.44 with a yield of around 0.53 with Céram membranes of MMCO of 300 kg·mol-1. Stationary ultrafiltration flux was around 64 L·h-1·m-2 at a volume reduction ratio of 9.