Ultrasound Treatment Affect Corn Steep Liquor Protein Hydrolysis and Biostimulatory Properties for Wheat Seeds Germination

Abstract

This study is dedicated to the application of renewable sources such as corn steep liquor (CSL) from wet corn milling as protein source (44.4 g/100g d. m.) for designing new bio-stimulants in sustainable wheat production. The ultrasound (US) pre-treatment of CSL (before enzymatic hydrolysis) was performed using low and high frequencies (37 kHz and 850 kHz, respectively) at 50 °C temperature for 30 min. Enzymatic hydrolysis of CSL was performed separately using a commercial alkaline protease preparations (1.05; 2.10; 5.00; 10.50; and 42.00 g/L) at optimal conditions (70 °C temperature and pH 9.0) as well as in combination with US. The effect of US on the degree of CSL protein hydrolysis and the changes in free amino acids (FAA) using ultrafast HPLC was investigated. Obtained results showed that US pre-treatment of CSL resulted in the increase of the total amount of hydrolyzed proteins (HP) on average by 30.0%. The application of US at a lower frequency (37 kHz) was more efficient for protein hydrolysis than the usage of high frequency (850 kHz). The highest HP concentration (17.48 g/L) was obtained using US (37 kHz) in combination with enzymes (2.10 g/L), while using only enzymes the content of HP was lower (12.48 g/L). The kinetics study of hydrolysis suggest that US treatment can significantly reduce the amount of enzyme achieving the same protein hydrolysis effect. The bio-stimulatory effect of selected CSL samples were tested in vivo on winter wheat seeds germination. Positive changes of CSL protein hydrolysates on the seed germination and especially on the root development have been obtained. This finding indicates that by-products of starch production could be promising source for bio-stimulants preparation.