1-Butyl-3-methylimidazolium acetate pretreatment of giant reed triggering yield improvement of biohydrogen production via photo-fermentation.

Ionic liquids (ILs) have been considered as promising alternatives to traditional reagent for lignocellulosic biomass pretreatment because of their tunable physicochemical and "green" properties. In the study, the influence of 1-Butyl-3-methylimidazolium acetate ([Bmim]acetate) pretreatment of giant reed on H2 yield improvement via photo-fermentation (PF) was evaluated. Under the optimal pretreatment conditions (6 g/L [Bmim]acetate at 70 °C for 4 h), the delignification of giant reed was up to 26.7 %. In addition, the sugar yield (9.5 g/L) and hydrogen yield (72.3 mL/g TS) from giant reed were enhanced by 1.7-fold and 61.7 % over those of untreated giant reed, respectively. Moreover, ternary analysis showed that retention time had the strongest effect on delignification, sugar yield and hydrogen yield of giant reed compared to pretreatment temperature and [Bmim]acetate loading. These experimental results indicated that [Bmim]acetate pretreatment of giant reed is an effective approach to enhance the hydrogen yield via PF.

Effect of 5-HMF and furfural additives on bio-hydrogen production by photo-fermentation from giant reed.

Substances harmful to photo-fermentative biological hydrogen production (PFHP) were produced during cellulose hydrolysis. This study aimed to evaluate the effect of by-products (5-hydroxymethylfurfural (5-HMF) and furfural) released from lignocellulose during enzymatic hydrolysis process on PFHP. The exist of 5-HMF inhibited the hydrogen production. However, 0.2 g/L furfural improved the hydrogen production by 19 % compared to no addition (511.6 mL) with a maximum concentration of nitrogenase (109.96 IU/L) at 96 h. Furthermore, a 18.7 % enhancement of hydrogen production was also observed when 0.2 g/L 5-HMF and furfural were mixed at a ratio of 1:1, while decrement of hydrogen production at higher addition was observed as well. Through the scatter matrix analysis, it was concluded that 5-HMF and furfural additives had significant effects on PFHP. This study gave an insight into effect of lignocellulosic by-products on biohydrogen production.

Comparison of three ionic liquids pretreatment of Arundo donax L. For enhanced photo-fermentative hydrogen production.

Ionic liquids (ILs) pretreatment has been regarded as a promising green way to treat lignocellulosic biomass. 1-Butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4), 1-allyl-3-methylimidazolium chloride ([Amim]Cl), and 1-Butyl-3-methylimidazolium Hydrogen Sulfate ([Bmim]HSO4) with different loadings (2, 4, 8, and 16 g/L) were adopted to pretreat the Arundo donax L.. 16 g/L [Bmim]HSO4 pretreated Arundo donax L. obtained the highest sugar yield of 7.9 g/L during the enzymatic hydrolysis and hydrogen yield of 106.1 mL/g TS during the photo-fermentation, which were 68.8 % and 35.3 % higher than those of untreated Arundo donax L., respectively. Moreover, volatile fatty acids (VFAs) distribution revealed that acetic acid was the main by-product during hydrogen production process with ILs pretreated Arundo donax L.. Besides, the relationship between sugar yield and hydrogen yield was the closest based on scatter matrix analysis. This study helps to understand of correlation between ILs pretreatment with the behavior of bioenergy production.

Towards high light conversion efficiency from photo-fermentative hydrogen production of Arundo donax L. By light-dark duration alternation strategy.

Suitable illumination project would help in achieving high light conversion efficiency (LCE) for photo-fermentation. This study proposed an improvement strategy for LCE of photo-fermentative hydrogen production (PFHP) with a photosynthetic consortium by adopting light-dark duration alternation. For this purpose, 6 projects (continues light, 24 h light + 24 h dark, 24 h dark + 24 h light, 48 h light + 48 h light, 48 h dark + 48 h light, and continues dark) light disturbances were carried out to estimate the strategy. The fluctuation of cell growth (OD660) was corresponded to the light-dark alternation. 24 h dark + 24 h light alternation achieved the maximum hydrogen yield (HY) of 390.9 mL/g TS cell (6.7 % higher than continuous light) and maximum improvement of LCE of 114.7%. Moreover, heat map analysis revealed that the light period after inoculation had the closest relation (Pearson's r = 1) with the average hydrogen production rate (HPR) of photo-fermentation. Besides, decreased dark period after inoculation would increase the hydrogen yield of photo-fermentation.