Role of plant protease in manure protein hydrolysis and biohydrogen production during dark fermentation

Nazifa, Tasnia Hassan (2024) Role of plant protease in manure protein hydrolysis and biohydrogen production during dark fermentation. Masters thesis, Memorial University of Newfoundland.

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Abstract

Protein-rich waste dark fermentation is challenging because protein degradation produces ammonia that inhibits anaerobic microorganisms. This thesis presents a study of the plant proteases role in manure protein degradation and hydrogen production in dark fermentation. The study used kiwi peel waste (KPW) and pineapple peel waste (PPW) as sources of protease enzymes (actinidin and bromelain, respectively) and Box-Behnken Design (BBD) and Response Surface Methodology (RSM) to evaluate the effects of multiple variables and identify optimal conditions. KPW and PPW reduced ammonia nitrogen by 64±0.65% and 72±0.48%, respectively, and increased protein degradation by 39±0.54% and 36±0.25%, respectively. Further investigations used BBD and RSM to optimize hydrogen production under inhibited methanogenesis. The maximum hydrogen yields were 510±7 and 385±7 mL g⁻¹ VS with KPW and PPW, respectively. In addition, the study includes a comparative analysis of biohydrogen production from protein-rich manure with pure proteins (albumin and casein), unveiling optimal conditions that resulted in high biohydrogen yields, up to 554±3 and 247±6 mL H₂ g⁻¹ VSalbumin with KPW and PPW, respectively, and 400±4 and 312±3 mL H₂ g⁻¹ VScasein with KPW and PPW, respectively. The thesis also explores the protease-induced structural and functional transformations by Scanning electron microscopy (SEM) and Fourier transform infrared Spectroscopy (FTIR) analyses, providing insights into the profound changes in the protein morphological and molecular composition, highlighting the effectiveness of KPW and PPW in disrupting manure protein structures to facilitate enhanced degradation and hydrogen production. The current study highlights the potential of using protein-rich waste for improving hydrogen yield in dark fermentation outcomes and establishes a foundation for future research into waste-to-energy conversion strategies.

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