Abstract
Objective: The objective of this study was to enrich therapeutic proteins and remove pollutants from dairy wastewater for establishing foam fractionation as a lucrative unit operation.
 Methods: Dairy wastewater collected from dairy industry was processed to fat-free dried protein waste mass diluted to 1-liter feed by distilled water in different concentrations and foam fractionated by sodium dodecyl sulphate (surfactant) to enriched proteins extract (foamate) in a foam fractionator. Foamate were analysed to quantify total proteins and lacto peroxidase respectively. The efficiency was evaluated by varying parameters like pH, initial waste and ionic concentrations, the waste-surfactant mass ratio of feed and flow rate of gas (N2) through feed solution by several experiments. Heat of desorption (λ) and mass transfer coefficient (K) were determined as indicators of adsorptive bubble separation to foam phase governed by Gibb’s equation of adsorption isotherm.
 Results: The process was optimized at pH 5.5, initial feed concentration 500μg/ml, waste–surfactant mass ratio (1.5:1), gas flow rate (350 ml/min) and ionic concentration 0.1 gram-mole of NaCL per litre of feed with enrichment factor (49.09), percent recovery (98.18%) observed in foamate. One natural preservative specifically lactoperoxidase was quantified by RP-HPLC analysis as 0.49% (w/w) of total proteins at optimal condition. Heat of desorption(λ), mass transfer coefficient(K)were determined 3140cal/mol and 12.68* 10-9 mol/cal/cm2/s respectively at pH 8.5, initial feed concentration 500μg/ml and gas flow rate 350 ml/min.
 Conclusion: The method may be a useful unit operation for recovery of biomolecules and removal of toxic pollutants from industrial wastewater for coming days.
Highlights
Worldwide milk production rising every year by more than 1% that reached around 800 tons in the year of 2017
The protein mass was diluted in the concentration range of 50-900 μg/ml in double distilled water and absorbance of each concentration was determined in a spectrophotometer(UV1800,Shimadzu,Japan) at wavelength 280 nm to draw the standard curve of protein waste powder solution essential for the analysis of total protein extracted in foamate
The maximum values were recorded with enrichment ratio (ER=49.09) and percent recovery (%Rp=98.18) for total protein as well as bovine lactoperoxidase (BLP) of 0.49% (w/w) in enriched protein extract at pH 5.5
Summary
Worldwide milk production rising every year by more than 1% that reached around 800 tons in the year of 2017. India will become the leading milk production country for the coming year, 2026. Under these circumstances, huge amount of dairy wastes will be generating from various dairy products such as milk, yoghurt, desserts and custards, cheese, butter, milk powders etc. Dairy wastewater contains a variety of therapeutic wastes along with other compounds [1,2,3] In this context, application of the lucrative technique for co-product recovery from dairy wastewater is very significant to serve the dual purpose for controlling environmental pollution as well as recovery of pharmaceutical and nutritional dairy waste such as the variety of proteins and other molecules for the health of man and animal kingdom. The amount of surface active molecules adsorbed can be quantitatively expressed by Gibb’s Equation of Adsorption Isotherm [4, 5]
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