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

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.

The Utilization of Food Waste: Challenges and Opportunities

“…Food waste with nutrients composition of 30-60% starch, 5-10% proteins and 10-40% (w/w) lipids makes food waste a promising raw material [6]. Chemical and biological/enzymatic methods can be performed for the recovery of nutrients from food waste in the form of carbon, nitrogen and phosphorus compounds after solubilisation of the waste matter [26,[46][47][48]. Studies have shown that food waste has high crude protein values, minerals, as well as other bioactive compounds of nutritional benefits and this food waste, can also be channelled into animal feed production thus increasing livestock productivity [2,49,50].…”

“…Most of the food waste matters requires hydrolytic enzymes such as glucoamylases, cellulases, Makanjuola proteases and phosphatases for their hydrolysis [6]. A sorghum bran based biorefining concept was developed by Makanjuola, Greetham [26] for the production of glucoamylase using Aspergillus awamori. The sorghum bran was hydrolyzed using the glucoamylase enzyme produced for the production of a sugarrich fermentation medium and a glucose concentration of 38.7 g/L from 200 g/L sorghum bran was obtained.…”

“…For the food waste generated, studies have been carried out to utilize food waste as raw materials for the production of a broad spectrum of commercially essential products, including: dietary fibre, livestock feed, biogas [22], biopolymers, bioplastic, biofuels (i.e., bioethanol, bio-butanol, biodiesel), enzymes [23,24], nutraceutical, single-cell proteins, [18], food flavors, bio adsorbents [25]. The production of chemicals, materials and energy can be derived from food waste [6] via a sustainable and environmentally friendly process to reduce its effect on the environment [26]. This review focused on the utilization of food waste for the production of value-added products, how effective food waste management could help minimize global food wastage, the impact of pandemic on food wastage, its challenges and opportunities.…”

Advances in Food and Byproducts Processing towards a Sustainable Bioeconomy

“…Likewise, enzymes entail a frequently studied end-product in fermentative bioconversions. Makanjuola et al [5] used sorghum bran, a processing waste rich in starch, for the secretion of glucoamylase in submerged fermentations using the fungal strain Aspergillus awamori . Cultivation parameters were evaluated to obtain maximum enzyme production, and subsequently hydrolysis experiments were performed, resulting in a glucose-rich solution for further involvement in microbial fermentation.…”