Effect of sequential twin screw extrusion and fungal pretreatment to release soluble nutrients from soybean residue for carotenoid production

Abstract

BACKGROUND: Soybean residue (okara) is an agricultural by-product, which is rich in protein and fiber. This study evaluated a novel sequential process which combined fungal pretreatment (F) and twin screw extruder (E), to hydrolyze okara. The sequence of the pretreatment steps, and extruder at screw speeds 200 rpm (200) or 600 rpm (600), were tested. Next, soluble nutrients were extracted to create Fokara, EFokara200, EFokara600, FEokara200 and FEokara600 okara media. RESULTS: All the prepared okara media could support the growth and carotenoid production by the yeast Rhodosporidium toruloides. This suggested that okara proteins and polysaccharides were successfully hydrolyzed by extrusion and fungal pretreatment, into soluble nutrients. Rhodosporidium toruloides accumulated the highest biomass of 23.7 mg mL −1 dry cell weight (DCW), when grown on FEokara600 media. This was higher as compared to commercial YPG (yeast extract-peptone-glycerol) media (18.7 mg mL −1 DCW). However, R. toruloides accumulated the highest carotenoid production of 13.2 g mL −1 when grown on EFokara200 media as the nutrient source. This was comparable to carotenoid production of 13.1 g mL −1 when R. toruloides was grown on YPG media. CONCLUSION: Extrusion in combination with fungal pretreatment, is a low cost process, to hydrolyze and re-use okara, for carotenoid production.

Engineering Sphingobium sp. to Accumulate Various Carotenoids Using Agro-Industrial Byproducts

“…A feasible strategy for meeting the challenge is to construct high-yield carotenoid microorganism by metabolic engineering that could use agro-industrial byproducts for reducing production cost and maintaining sustainable development. Glycerol, corn steep, and okara have attracted interest as raw materials for microbial to production of value-added chemicals and compounds ( Liu et al, 2012a ; Lee et al, 2019 ; Zhao et al, 2019 ; Kang et al, 2020 ). Crude glycerol is a byproduct generated from biodiesel production; okara and corn steep liquor are generated as byproducts during the manufacture of soymilk and corn starch.…”

Soybean‐based concept biorefinery

“…Lee et al 84 . used the residue of soy in a new sequential process that utilized fungal pre‐treatment and twin‐screw extrusion to hydrolyze okara, aiming to free the soluble nutrients of the soy residue in the production of carotenoids.…”

Gene source selection as a metabolic engineering tool for naringenin production in Saccharomyces cerevisiae

“…From the commercial nitrogen sources 3% yeast nitrogen with amino acids and 3% peptone media were prepared. Okara was valorized by solid-state fermentation using Rhizopus oligosporus 169 . The nutrients are extracted and diluted with distilled water in order to make the final okara content 3%.…”

“…It is a major waste product that is mainly disposed into landfills. Worldwide 14 million tons of okara are generated annually and it is one of the main agro-wastes in Southeast Asia 169 . However, okara has highly nutritious components that can be hydrolyzed into simple sugars, amino acids and minerals 173 .…”