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In this paper, poly β-hydroxy butyrate (PHB) was extracted from H2 production fermentation residue of photosynthetic bacteria, the best separation and extracted conditions was optimized, the interaction of different factors affecting the extraction rate of the PHB was analyzed, the molecular weight and the purity of extracted PHB were also studied. The results showed that the best method of cell broken were multi-bead shaker for 10 minutes, then boiled and frozen broken at -5°C; With chloroform and ethanol extracting PHB, the best extracted conditions were extracted temperature 40°C, extracted time 90 min, PHB production could reached 7.6% of dry cell weight, the purity of PHB reached 88.2%; Using response surface method analysis the correlation of different factors affecting PHB extraction rate, extracted pH value was the most significant factor, followed by cell concentration, and extracted temperature was the weakest factor, the best extracted conditions calculated were extracted pH value 8.2, cell concentration 475mg /L, extracted temperature 44°C, the maximum extracted rate of PHB reach 8.13% of cell dry weight; The molecular weight of extracted PHB samples among 0.36~0.45×106 daltons, GC analysis showed that the relative peak area ratio of extracted PHB sample and standard was 0.96:1, the purity was coincident with the standard PHB to meet the industrial application requirements.

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Stress corrosion cracking (SCC) behaviors of Mg-7Al-0.3Mn alloy in 0.21M K2CrO4+0.6M NaCl solution and in air were studied using slow strain rate test (SSRT). The effect of electrode potential on SCC behaviors of the alloy was investigated in 0.21M K2CrO4+0.6M NaCl solution during SSRT. The fractographs of the alloy tested in air and in the solution were observed. These results indicated that SCC of the alloy was related to the hydrogen embrittlement and pitting corrosion. The pitting corrosion was the cause of crack initiation, and the hydrogen embrittlement leaded to crack propagation.