Enzymatic hydrolysis and fermentation of soy flour to produce ethanol and soy protein concentrate with increased polyphenols

Agrawal, Ruchir Manoj

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https://hdl.handle.net/2142/113959 Copy

Description

Title

Enzymatic hydrolysis and fermentation of soy flour to produce ethanol and soy protein concentrate with increased polyphenols

Author(s)

Agrawal, Ruchir Manoj

Issue Date

2021-10-19

Director of Research (if dissertation) or Advisor (if thesis)

Takhar, Pawan S

Committee Member(s)

• Miller, Michael J
• Singh, Vijay

Department of Study

Food Science & Human Nutrition

Discipline

Food Science & Human Nutrition

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Soy protein concentrate
• fermentation
• ethanol
• raffinose
• enzymatic hydrolysis

Abstract

Defatted soybean flour (DSF) is a protein-rich ingredient; however, it contains 30-35% carbohydrates, which is made up in parts by sucrose, flatulence-causing oligosaccharides, and water-insoluble cell-wall polysaccharides. A process was developed to produce soy protein concentrates (SPC) by substantially hydrolyzing these carbohydrates with the help of enzymes into water-soluble saccharides and monomeric sugars, which were simultaneously utilized by Saccharomyces cerevisiae for fermentation into ethanol. The enzyme mixture consisted of a cellulase blend, pectinase blend, and α-galactosidase. The effect of process time on SPC protein concentration, overall protein recovery, carbohydrate hydrolysis, yeast growth, ethanol concentration, and total polyphenol concentration of SPC and hydrolysate were evaluated. Control and enzymes-only (EO) systems were maintained in conjunction with the enzymes + yeast (EY) system to individually assess the impact of isoelectric precipitation of soy proteins and enzymatic hydrolysis of carbohydrates without yeasts in the production of SPC. After 12.25 hours of EY process, 100 g of dry DSF produced 68.45 g dry SPC containing 72.23 ± 0.25% protein and 384 mL hydrolysate containing 9.76 ± 0.05 mg/mL ethanol. Protein recovery from DSF in the form of SPC was 84.4 ± 0.4%. Viable yeast count steadily declined from 1.6 ± 0.1×106 CFU/mL slurry at the start of the process to 7.9 ± 1.3×105 CFU/mL slurry after 12.25 hours. Flatulence causing raffinose-series-oligosaccharides were completely hydrolyzed into their monomeric sugars during this process. Total soluble carbohydrates in the EY treatment were consistently lower than control and EO treatment, suggesting that the yeasts were able to ferment sugars as they were becoming available. Total polyphenol concentration (TPC) of SPC increased more than twofold from 1.21 ± 0.04 mg gallic acid equivalent (GAE)/g dry SPC in control to 3.06 ± 0.03 mg GAE/g dry SPC in EY treatment. Similarly, hydrolysate TPC increased twofold from 179 ± 1 μg/mL in control to 371 ± 6 μg/mL in EY treatment. Thus, this novel process led to a protein and polyphenol-rich and reduced-carbohydrate SPC along with polyphenol and ethanol-containing hydrolysate.

Graduation Semester

2021-12

Type of Resource

Thesis

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http://hdl.handle.net/2142/113959

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Copyright 2021 Ruchir Agrawal

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