Fermentative hydrogen production from pretreated biomass: A comparative study

The aim of this work was to evaluate the potential of employing biomass resources from different origin as feedstocks for fermentative hydrogen production. Mild-acid pretreated and hydrolysed barley straw (BS) and corn stalk (CS), hydrolysed barley grains (BG) and corn grains (CG), and sugar beet extract (SB) were comparatively evaluated for fermentative hydrogen production. Pretreatments and/or enzymatic hydrolysis led to 27, 37, 56, 74 and 45 g soluble sugars/100 g dry BS, CS, BG, CG and SB, respectively. A rapid test was applied to evaluate the fermentability of the hydrolysates and SB extract. The thermophilic bacterium Caldicellulosiruptor saccharolyticus showed high hydrogen production on hydrolysates of mild-acid pretreated BS, hydrolysates of BG and CG, and SB extract. Mild-acid pretreated CS showed limited fermentability, which was partially due to inhibitory products released in the hydrolysates, implying the need for the employment of a milder pretreatment method. The difference in the fermentability of BS and CS is in strong contrast to the similarity of the composition of these two feedstocks. The importance of performing fermentability tests to determine the suitability of a feedstock for hydrogen production was confirmed.     

几株啤酒酵母的筛选及发酵性能比较*

啤酒酵母是啤酒酿造的灵魂,可以直接影响啤酒品质。在啤酒酿造过程中,由于啤酒酵母被多次传代和保藏,造成优良菌种发酵性能衰退等问题,导致发酵不彻底,影响最后啤酒的风味质量。为此以8株Lager型啤酒酵母为出发菌株,通过平板分离纯化获得80株分离菌株,再经过三角瓶发酵初筛和复筛、发酵罐中试发酵实验最终获得了8株发酵性能优良的啤酒酵母。其中,6株酵母可应用于酿造双乙酰含量低于0.1 mg/L的啤酒;3株酵母发酵度高于70%,适合酿造干啤酒;1株酵母发酵度低于50%,适合酿造低醇啤酒。在风味方面:1株酵母酿造的啤酒醇酯比为3.3,啤酒酯香味较突出;另1株酵母酿造的啤酒醇酯比为4.5,啤酒高级醇含量较高。8株经过选育的啤酒酵母发酵特征明显,便于精酿啤酒厂实际应用。