Abstract Methane (CH 4 ) can be mitigated through directly inhibiting methanogen activity and starving methanogens by hydrogen (H 2 ) sink. Three types of mechanism (i.e. bromoethanesulphonate (BES), nitrate and emodin) and doses of CH 4 mitigation agents were employed to investigate their pathways of CH 4 inhibition. Results indicated that both BES and emodin inhibited CH 4 production and altered H 2 balance, which could be accompanied by decreased dry matter disappearance (DMD), fractional rate of gH 2 formation, volatile fatty acid (VFA) production, ability to produce and use reducing equivalences and molecular H 2 , and increased final asymptotic gH 2 production, time to the peak of gH 2 , discrete lag time of gH 2 production and fermentation efficiency. However, emodin decreased gas volume produced by rapidly fermentable components of substrate and the rate of fermentation at early stage of incubation, while BES supplementation inhibited gas volume produced by both rapidly and slowly fermentable components of substrate and the rate of fermentation at middle or late stage of incubation. The nitrate supplementation inhibited CH 4 production without affecting VFA profile, because of its dual role as H 2 sink and being toxic to methanogens. Nitrate supplementation had more complicated pattern of fermentation, VFA production and profile and H 2 balance in comparison to BES and emodin supplementation.
Two-line hybrid glutinous sorghum liquor was used as base liquor and then soaked separately or the whole juice of Citrus reticulata,Satsuma mandarin(red),Navel orange and Satsuma mandarin(yellow) to produce liqueur with alcohol content(v/v) as 20 % to 40 % and sugar content(g/L) as 210 to 360 g/L.Through the orthogonal design experiments of the key technical operation and the flavor regulation,the optimum technical conditions were summed up as follows: addition of 260 g syrup in 1 L 60 % base liquor for 40 h steeping at 40 ℃,and the best blending parameters: sugar degree as 270,pH as 4.5,and 20 %Vol alcohol content.The product liqueur was golden yellow in color and clean and transparent with harmonious liquor body and particular citrus aroma and pure and enjoyable taste.
Through investigating the characters of several acetic acid bacteria in citrus vinegar fermentation, QY7009 strain was obtained that was appropriate for citrus vinegar fermentation. The result indicated that the acid production speed and the alcohol conversion rate of QY7009 strain in citrus wine were higher than the strains of AS1.41 and Huniang1.01. Alcohol conversion rate of QY7009 strain in the citrus wine with 6% alcohol reached 87%.
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