Thin Stillage and Soybean Hulls Valorization for Their Expanded Applications

Monday, April 29, 2024

10:35 AM – 10:55 AM EDT

Room: 518a

Presenting Author(s)

Bhawana Khadka (she/her/hers)

Graduate Student
South Dakota State University
Brookings , SD, United States

Co-Author(s)

Santosh Thapa, MS in Microbiology (he/him/his)

Graduate Student
South Dakota State University, SD, United States

Co-Author(s)

Bs

Brady steffen

Undergraduate Student
South Dakota State University, United States
Bishnu Karki, PhD

Assistant Professor
South Dakota State University
Brookings, SD, United States

Abstract: Thin stillage (TS) is a nutrient rich byproduct of corn-based ethanol industry. Due to its high moisture, TS is concentrated via a series of evaporation cycles, which is highly energy intensive, and its application is limited as animal feed supplements. Alternatively, fungal fermentation can be used to add value to TS. Soybean hull (SBH) is another underutilized lignocellulose-rich byproduct from soybean processing industries. Mixing TS with SBH can balance the carbon/nitrogen ratio necessary for fungal growth. The objective of this study is to explore fungal fermentation as an alternative to advance the industrial use of TS by enabling nutrient extraction.

Method: Submerged fermentation of TS and TS supplemented with SBH (TS+SBH) were done by using Aureobasidium pullulans (Ap), Aspergillus oryzae (Ao), Trichoderma reesei (Tr) and Aspergillus niger (An) at 30 °C for 120 h. Sampling was done in 24 hours interval and analyzed for LECO protein (CP), total phenolic content (TPC), phytic acid, crude fiber, reducing sugar and total carbohydrates.

Results: TS contained 8.98% dry matter, 33.23% CP, 14.72 mg GAE/g TPC and 0.47 g/100 g phytic acid on dry basis. All fungal strains significantly increased % CP of TS and TS+SBH after 48 h but % CP declined as fermentation continued. Ao, Tr and An significantly increased TPC of TS by 100.75%, 49.31% and 45.6% respectively, while Tr and An increased the TPC in TS+SBH by 50.14% and 53.7% respectively. Ap fermentation decreased phytic acid significantly in TS by 33.33% while Ap, Ao and An decreased phytic acid significantly by 35%, 42.2% and 43.2% respectively in TS+SBH fermentation. Results for analysis of crude fiber, crude fat, total carbohydrates and reducing sugars are under process. Overall, fungal fermentation of TS with SBH improved the nutritive value of both substrates and can be used to produce high value end products.