Abstract

The aim of the present work is the study of the feasibility of a solid carob waste valorization from the Lebanese food industry using dark fermentation for a second-generation biohydrogen production. The preliminary experiments conducted in 125-mL glass bottles showed that the most effective initial pH was 6.0 and the highest hydrogen yield was 1.38 mol H₂/mol hexose consumed for sucrose, followed by 1.32 mol H₂/mol hexose consumed for carob waste. However, using 2-L bioreactor with pH control, hydrogen productivity were enhanced using carob waste compared to glucose. Two ways of improving dark fermentation were studied. First, the importance of nitrogen source was demonstrated. The hydrogen yield (1.15 ± 0.05 mol H₂/mol hexose consumed) were clearly lower with the iron medium compared to the complete medium (1.28 ± 0.04 mol H₂/mol hexose consumed). Second a simplified medium including only iron and nitrogen was prepared, and by using this medium an improvement of the hydrogen yield were recorded (1.22 ± 0.03 mol H₂/mol of sugar consumed). Then, particle size reduction from 5.0 to 2.5 mm enhanced the hydrogen yield up to 1.37 mol H₂/mol hexose consumed, and productivity up to 0.089 mol H₂/mol hexose consumed/h.

摘要

本工作的目的是研究利用暗发酵生产第二代生物氢的黎巴嫩食品工业固体角豆废料增值的可行性。在 125-mL 玻璃瓶中进行的初步实验表明，最有效的初始 pH 值为 6.0，最高的氢气产量是蔗糖消耗的1.38 mol H ₂ /mol 己糖，其次是角豆废料消耗的1.32 mol H ₂ /mol 己糖。然而，使用具有 pH 控制的 2-L 生物反应器，与葡萄糖相比，使用角豆废料提高了氢气的生产率。研究了两种改善暗发酵的方法。首先，证明了氮源的重要性。氢气产率 (1.15 ± 0.05 mol H _{2与完全培养基（1.28 ± 0.04 mol H 2} /mol 己糖消耗）相比，铁培养基的用量明显较低。其次，制备了仅包含铁和氮的简化培养基，并且通过使用这种培养基，记录了氢产率的提高（1.22 ± 0.03 mol H ₂ /mol 消耗的糖）。然后，粒径从 5.0 减小到 2.5 mm，氢气产率提高到 1.37 mol H ₂ /mol 己糖消耗，生产率提高到 0.089 mol H ₂ /mol 己糖消耗/小时。