Gracilaria lemaneiformis Bory is an economically important alga that is primarily used for agar production.Although tetraspores are ideal seeds for the cultivation of G.lemaneiformis,the most popular culture method is currently based on vegetative fragments,which is labor-intensive and time-consuming.In this study,we optimized the conditions for tetraspore release and evaluated the photosynthetic activities of different colonies formed from the branches of G.lemaneiformis using a PAM(pulse-amplitude-modulated) measuring system.The results showed that variations in temperature and salinityhad significant effects on tetraspore yield.However,variations in the photon flux density(from 15 μmol m-2 s-1 to 480 μmol m-2 s-1) had no apparent effect on tetraspore yield.Moreover,the PAM-parameters Y(I),Y(Ⅱ),ETR(I),ETR(Ⅱ) and Fv/Fm of colonies formed from different branches showed the same trend:parameter values of first generation branches>second generation branches>third generation branches.These results suggest that the photosynthetic activities of different colonies of branches changed with the same trend.Furthermore,photosynthesis in G.lemaneiformis was found to be involved in vegetative reproduction and tetraspore formation.Finally,the first generation branches grew slowly,but accumulated organic compounds to form large numbers of tetraspores.Taken together,these results showed that the first generation branches are ideal materials for the release of tetraspores.
Acid, alkali, heat-shock, KNO3 and control pretreatment methods applied to anaerobic sludge were evaluated for their ability to selectively enrich the marine hydrogen-producing mixed microflora. Sea-water culture medium was used as the substrate. The hydrogen yield of pretreated microflora was higher than that of the un-pretreated control (P < 0.05). Among the pretreatment methods studied, heat-shock pretreatment yielded the greatest hydrogen production, which was 14.6 times that of the control. When the effect of initial pH on hydrogen production of heat-shock pretreated samples was studied, hydrogen was produced over the entire pH range (pH 4 - 10). The hydrogen yield peaked at initial pH 8 (79 mL/g sucrose) and then steadily decreased as the initial pH increased. Sucrose con-sumption was high at neutral initial pH. During the process of hydrogen production, pH decreased gradually, which indicated that the acquired microflora consisted of acidogenic bacteria.
CAI JinLingWANG GuangCeLI YanChuanZHU DaLingPAN GuangHua
