Waste generation demands that measures must be put in place in order to avert their detrimental effect to the environment. Bioconversion of agricultural waste to useful products like enzyme is a welcome development. Amylase production by Aspergillus niger via submerged fermentation of fruit wastes such as pineapple, orange, banana, cucumber and watermelon was investigated. Biomass of A. niger, amylase produced and pH of the fermenting fruit waste media were determined using standard techniques during submerged fermentation. From the data obtained Banana waste medium produced the highest yield of A. niger amylase (259.00 ± 1.23 U/mL) compared to other waste media at 4 d of fermentation. Amylase yield from Banana waste medium was significantly higher compared with the other fruit wastes (p < 0.05). Among the various supplemented nitrogen sources in the Banana waste medium, ammonium nitrate gave the highest amylase yield of 881.00 ± 16.97 U/mL while the least (549.5 ± 20.51 U/mL) was from potassium nitrate medium. Thus, the study revealed that A. niger can be used for amylase production from fruit waste and optimal yield can be enhanced by supplementing the medium with ammonium nitrate.

Formic acid is one of the major inhibitory compounds present in hydrolysates derived from lignocellulosic materials, the presence of which can significantly hamper the efficiency of converting available sugars in the hydrolysates to bioethanol. The influence of different nitrogen sources supplemented media on bioethanol fermentation with Saccharomyces spp in the presence of formic acid was studied. The addition of ammonium sulphate and urea significantly increased cell number, glucose utilization, ethanol and glycerol production when compared with control media. It was observed that supplementation with nitrogen sources contributed assimilable nitrogen for the yeast strains growth when stressed with formic acid. The best concentration of nitrogen to be utilized by yeast was found to be 0.80 gN/L. The maximum cell numbers were 8.17± 0.23x 107 and 8.68± 0.16x 107 cells/mL for ammonium sulphate medium while control had the least of 4.00± 0.20x 107 and 4.97± 0.08x 107 cells/mL for S. cerevisiae NCYC2592 and S. arboricolus 2.3319 respectively. Ethanol accumulation increased with the consumption of glucose. The maximum ethanol production were 20.49 ± 1.24 and 19.74± 0.89 g/L using ammonium sulphate for S. cerevisiae NCYC2592 and S. arboricolus 2.3319 respectively. There was significant difference in ethanol production when the nitrogen sources were compared with the control medium (p< 0.05). The highest glycerol produced were 2.21 ± 0.04 and 3.11± 0.05 g/L using ammonium sulphate for S. cerevisiae NCYC2592 and S. arboricolus 2.3319 respectively. The conclusion was that yeast tolerance to formic acid and ethanol production could be achieved when fermentation medium is supplemented with nitrogen sources specifically ammonium sulphate.Keywords: Lignocellulose, inhibitors, Saccharomyces, fermentation, yeast, biofuel

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