Biosynthesis of Polyhydroxyalkanoate （PHA） by Hydrogenophaga sp. Isolated from Soil Environment during Batch Fermentation

In this work, sucrose utilizing microbes from soil were screened to evaluate their ability for accumulation of biopolymer of polyhydroxyalkanoate （PHA）. Among 72 isolates were transferred to mineral salt medium （MSM）, 33 strains can be grown on sucrose agar medium. However, only one strain showed a strong black color for Sudan Black and gave positive result for Nile blue A. Identification by 16S rDNA nucleotide sequence homology of the isolate showed very closely to Hydrogenophaga sp. （99% identify）. To consider PHA production, the isolate was grown in the medium containing sucrose as a sole carbon under controlled conditions of 35 ℃ and at pH 7. Maximum dry cell weight （DCW） and PHA production were obtained at 3.61 g/L and 2.41 g/L after 36 and 42 h batch fermentation. Sucrose uptake measured in term of total organic carbon （TOC） showed at 14.73 g within 48 h. The highest PHA was 68.15% （gPHA/gDCW） giving maximum PHA yield （YP/s） of 0.17 （gPHA/gs ） and a productivity of 0.057 gPHA/L.h. This highlights the potential of microbial resources in soil environment and may be an exploitable application for the industrial production of PHA.

褐藻胶裂解酶产生菌的分离鉴定及产酶发酵优化

对一株从腐烂海带中筛选得到的产褐藻胶裂解酶的菌株进行鉴定,并对其产酶条件进行发酵优化。经形态学、生理生化特征和分子生物学鉴定,将其鉴定为盐单胞菌属,并命名为Halomonas sp.WF6。通过在摇瓶培养水平上进行单因素和多因素正交试验,确定褐藻胶裂解酶产生菌WF6的最适产酶培养基为:褐藻酸钠6.0g/L,蛋白胨5.0g/L,酵母粉2.5g/L,NaCl30g/L,K^+5 mmol/L。进而采用最适培养基进行产酶条件的优化,优化后的发酵产酶条件为:初始pH8.0,培养温度25℃,接种量为2%,摇瓶装液量30 ml/250 ml,培养时间39 h。优化后的褐藻胶裂解酶酶活达117.66 U/ml,是优化前的2.1倍。该酶对褐藻酸钠的酶解产物主要由聚合度为二和三的褐藻寡糖组成。