The potential of using sorghum milling waste for the development of a biorefining strategy for the production of bioethanol was investigated. Both red and white sorghum were processed using a traditional Nigerian wet-milling process to sorghum flour. The sorghum milling waste, sorghum bran, was hydrolysed using both enzymatic and dilute acid hydrolysis to produce a generable fermentation feedstock. The hydrolysates were subsequently investigated for fermentative biofuel production. Following a hydrolysis step, a medium containing ~ 61 g/L glucose was obtained. Trace presence of inhibitors was detected in the hydrolysates and sufficient nitrogen content to support microorganism growth and bioethanol production. In test bioethanol production experiments using the sorghum milling waste derived hydrolysates only, 24.35 g/L bioethanol was produced by a yeast Kluyveromyces marxianus, equivalent to a yield of 0.15 gram bioethanol per gram of sorghum milling waste.

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Submerged substrate fermentation of Jatropha seed cake, a by-product of oil extraction from Jatropha curcas seed was carried out using Aspergillus terreus for the production of itaconic acid. The Jatropha seed cake was initially converted into fermentable sugars by dilute acid hydrolysis using 50% sulphuric acid. The rate of hydrolysis was 1.04 gL -1 . The fermentation process was carried out at room temperature, agitation of 400 rpm and three physico-chemical parameters (pH, inoculum size and substrate concentration) were varied. Itaconic acid and glucose assays were carried out by spectrophotometry and Dinitrosalicylic acid methods respectively daily. Maximum yield of itaconic acid was 48.70 gL -1 at 5 ml of inoculum size, 50% substrate concentration and pH 1.5. The residual glucose concentration increased for the first two days of fermentation after which it began to decrease as the itaconic acid concentration increased. The least concentration of itaconic acid observed was 6.00 gL -1 , obtained after 24 hours of fermentation with 4 ml inoculum size, 50% substrate concentration and at pH 1.5. The findings of this work indicate that Jatropha curcas seed cake is a suitable substrate for itaconic acid production.

PurposeBambara groundnut is a hard-to-cook grain and this has limited its utilisation to some extent. However, the grain is a good source of phytochemicals with antioxidant properties. This study investigated the total phenol content, antioxidant, anti-inflammatory and anti-microbial potentials of hot-water extract of four Bambara groundnuts differentiated by their seed coats (cream, black, maroon and brown).Design/methodology/approachBambara grains were heated in water at a ratio 1:20 (w/v) and the grains brought to boiling in a controlled water bath. As soon as boiling started, the temperature was reduced to 90 °C to reduce the evaporation rate. The extracts were withdrawn within 30 min, which was chosen from a preliminary study where beyond this time, the extract was drying off and the amount of solution obtained was not sufficient for the initial run. Grain colour and composition and antioxidant, antimicrobial and anti-inflammatory properties of the extract were determined using standard methods.FindingsProtein (20.57–26.31%) and carbohydrate (55.43–61.09%) were the major components of the grain. Grain type and boiling time generally affected the total phenolic content of the extract. Cream Bambara displayed substantially lower total phenolic content at all boiling times compared with the maroon, brown and black Bambara groundnuts. The total flavonoid contents and total phenolic contents of the Bambara groundnut extracts were dependent on the boiling time and type of grain. The extracts showed no activity against Candida albicans, but the maroon coat Bambara demonstrated a peak inhibition of 6.00 mm against Escherichia coli. The total phenolic, flavonoid contents and the antioxidant properties of the grains generally followed the order Maroon > Black > Brown.Originality/valueThis study has demonstrated the possibility of promoting the use of Bambara groundnut beyond the current level of usage by using simple processing method of boiling to extract phytochemicals with medicinal properties.