Abstract
Large-scale manufacturing of soybean proteins results in huge volume of “wastewater” which contains substantial amount of β-amylase, and the recovery of β-amylase has potential high value. In order to evaluate the feasibility and effect of novel hybrid Ultrafiltration (UF) method against the normal method, the pretreated effluent was concentrated by a low molecular weight cut off (MWCO) 3 kDa UF membrane firstly, terminated at Volume Concentration Ratio (VCR) of ca.7. To this UF retentate was then precipitated by adding 1.2M (NH4)2SO4 to remove other proteins. The supernatant obtained following centrifugation was purified through a further higher 30 kDa MWCO UF membrane, which ended at VCR of ca.10. The prepared was purified 4.8 fold, with an enzyme activity concentration ratio of 61, and is associated with 74% combined recovery for the enzyme activity, giving a final specific activity of 14 U/mg (674 U/mL), of which enzyme activity is fully enough for the industrial applications. Preliminary data of this research indicate that this could be an effective method for treating kinds of related protein wastewaters.
Highlights
Isolated Soy Protein (ISP) is one of the most important and widely used plant proteins, which in 2013 witnessed a production capacity of ca. 600 k tons in China
Manufacturing one ton of ISP results in ca. 40 tons of whey wastewater, which contains up to 8 g L-1 protein as well as oligosaccharides [1]. Such soybean whey wastewater possesses high Biochemical Oxygen Demand (BOD) values and by legislation cannot be discharged into the environment directly
The crude effluent is turbid (Table 1), resulting from causes like, (a) prior to the generation of this wastewater, the soybean protein isolate is precipitated at pH 4.5, a typical PI value for the major soybean proteins, and so is prone to further precipitation for slightly shifted solubility of the same proteins; and (b) the total solid material is as high as 2.5% (Table 1)
Summary
Isolated Soy Protein (ISP) is one of the most important and widely used plant proteins, which in 2013 witnessed a production capacity of ca. 600 k tons in China. 40 tons of whey wastewater, which contains up to 8 g L-1 protein as well as oligosaccharides [1]. Manufacturing one ton of ISP results in ca. Such soybean whey wastewater possesses high Biochemical Oxygen Demand (BOD) values and by legislation cannot be discharged into the environment directly. A substantial proportion of these whey proteins is β-amylase (α-1,4-glucan maltohydrolase; EC.3.2.1.2), an exo-hydrolase that releases β-maltose from non-reducing ends of α-1,4-linked polyglucans and oligoglucans until encountering the first α-1,6-branching point [3]. While β-amylase mixed with pullulanase has been found to convert starch to high maltose syrup [4]
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