The Development of a Sorghum Bran-Based Biorefining Process to Convert Sorghum Bran into Value Added Products.

Oyenike Makanjuola,Darren Greetham,Xiaoyan Zou,Chenyu Du

doi:10.3390/foods8080279

Oyenike Makanjuola, Darren Greetham + Show 2 more

Open Access

https://doi.org/10.3390/foods8080279

Copy DOI

Abstract

Sorghum bran, a starch rich food processing waste, was investigated for the production of glucoamylase in submerged fungal fermentation using Aspergillus awamori. The fermentation parameters, such as cultivation time, substrate concentration, pH, temperature, nitrogen source, mineral source and the medium loading ratio were investigated. The glucoamylase activity was improved from 1.90 U/mL in an initial test, to 19.3 U/mL at 10% (w/v) substrate concentration, pH 6.0, medium loading ratio of 200 mL in 500 mL shaking flask, with the addition of 2.5 g/L yeast extract and essential minerals. Fermentation using 2 L bioreactors under the optimum conditions resulted in a glucoamylase activity of 23.5 U/mL at 72 h, while further increase in sorghum bran concentration to 12.5% (w/v) gave an improved gluco-amylase activity of 37.6 U/mL at 115 h. The crude glucoamylase solution was used for the enzymatic hydrolysis of the sorghum bran. A sorghum bran hydrolysis carried out at 200 rpm, 55 °C for 48 h at a substrate loading ratio of 80 g/L resulted in 11.7 g/L glucose, similar to the results obtained using commercial glucoamylase. Large-scale sorghum bran hydrolysis in 2 L bioreactors using crude glucoamylase solution resulted in a glucose concentration of 38.7 g/L from 200 g/L sorghum bran, corresponding to 94.1% of the theoretical hydrolysis yield.

Highlights

The increasing concerns about global energy shortages and environmental pollution have encouraged research on the development of biorefining strategies for the conversion of renewable raw materials into value added products
Three milling processes using a peanut butter maker, blender and knife mill were examined for separating starch from sorghum bran
When the substrate concentration was increased to 12.5%, glucoamylase production was enhanced to 37.6 units per mL (U/mL), but the fermentation time was extended to 115 h

Summary

Introduction

The increasing concerns about global energy shortages and environmental pollution have encouraged research on the development of biorefining strategies for the conversion of renewable raw materials into value added products. Sorghum (Sorghum bicolor) is a cereal plant of the grass family Gramineae which originates from Africa [1] It is the 5th most important crop cereal in the world in terms of its acreage and production [2]. Sorghum grains are cleaned, conditioned, tempered and debranned in grain hulliers to remove the outermost fibrous layer. It is milled and sieved (dry milling process) to obtain a flour fraction using a Buhler mill [4]

Methods

Results

Conclusion