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1.
Peng Wang Zhen Chen Juan Li Li Wang Guohong Gong Genhai Zhao Hui Liu Zhiming Zheng 《Annals of microbiology》2013,63(3):957-964
The production of L(+)-lactic acid (LA) by Rhizopus oryzae immobilized in polyvinyl alcohol (PVA) was investigated. To decrease diffusional resistance, we modified the PVA gel through the addition of sodium alginate and phosphate esterification. The production of L(+)-LA improved notably in the immobilized Rhizopus oryzae. Maximum L(+)-LA production (106.27 g/L), with a yield of 73.1 % and rate of 2.95 g/L·h, was obtained at a temperature of 38 °C, 6 % PVA, and 0.8 % sodium alginate. The immobilized R. oryzae was stable in 14 serial-batch cultures using non-growth medium. The immobilized beads also displayed good tolerance to low temperature and long-term storage at 4 °C with the preservation of biochemical properties. 相似文献
2.
Zhu Genhai Bohnert Hans J. Jensen Richard G. Wildner Günter F. 《Photosynthesis research》1998,55(1):67-74
Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) (EC 4.1.1.39) not only catalyzes carboxylation and oxygenation of ribulose-1,5-bisphosphate (RuBP), but it can also act either as an epimerase or isomerase converting RuBP into xylulose-1,5-bisphosphate (XuBP) or 3-ketoarabinitol-1,5-bisphosphate (KABP), respectively, a process called misfire. XuBP is formed as a result of misprotonation at C3 of the RuBP-enediol. It is released from Rubisco active sites and accumulates in the reaction mixture. Increasing the amounts of CO2 or O2 decreases XuBP production. However, KABP synthesis, which has been proposed to be only a product due to C2 misprotonation of the RuBP-endiol, is dependent upon the presence of O2. KABP remains tightly bound to Rubisco active sites after its formation, causing the loss of Rubisco activity (fallover). The results suggest that the non-stabilized form of the peroxy-intermediate in the oxygenase reaction can be converted in a backreaction to KABP and molecular oxygen. The stabilization of the peroxy-intermediate due to the presence of Mn2+ instead of Mg2+ eliminates the formation of KABP. 相似文献
3.
An effective method for production of L-tryptophan from hair acid hydrolysis wastewater (HHW) containing L-serine was developed by recombinant tryptophan synthase. This study provides us with an alternative HHW utilization strategy. Tryptophan synthase could efficiently convert L-serine contained in HHW to L-tryptophan at pH 8.0, 40°C and Tween-80 of 0.04%. The enzyme also showed high tolerance to ammonium chloride, a component in HHW. In a scale up study, L-serine conversion rate reach 95.1% with a final L-tryptophan concentration of 33.2 g l(-1). 相似文献
4.
Zhemin Li Genhai Zhao Hui Liu Yugang Guo Hefang Wu Xiaowen Sun Xihua Wu Zhiming Zheng 《Journal of industrial microbiology & biotechnology》2017,44(7):973-985
Prenylated quinones, especially menaquinones, have significant physiological activities, but are arduous to synthesize efficiently. Due to the relaxed aromatic substrate specificity and prenylation regiospecificity at the ortho- site of the phenolic hydroxyl group, the aromatic prenyltransferase NovQ from Streptomyces may be useful in menaquinone synthesis from menadione. In this study, NovQ was overexpressed in Pichia pastoris. After fermentation optimization, NovQ production increased by 1617%. Then the different effects of metal ions, detergents and pH on the activity of purified NovQ were investigated to optimize the prenylation reaction. Finally, purified NovQ and cells containing NovQ were used for menadione prenylation in vitro and in vivo, respectively. Menaquinone-1 (MK-1) was detected as the only product in vitro with γ,γ-dimethylallyl pyrophosphate and menadione hydroquinol substrates. MK-3 at a concentration of 90.53 mg/L was detected as the major product of whole cell catalysis with 3-methyl-2-buten-1-ol and menadione hydroquinol substrates. This study realized whole cell catalysis converting menadione to menaquinones. 相似文献
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杭州西湖初步治理后的浮游植物现状 总被引:10,自引:0,他引:10
本文记录了杭州西湖初步治理后的浮游植物种类组成、相似性、数量分布与环境理化因子的关系,以及根据指示种类评价了西湖水质。在1985年2月至1986年2月周年调查的20个站位中,共鉴定了浮游植物7门92属229种、变种和变型;其中蓝藻门19属39种;绿藻门35属87种8变种1变型;硅藻门24属54种7变种1变型等。西湖浮游植物的数量分布以外湖最高,年均值为529.1×105个/L,三潭内湖最低,仅1.76×105个/L。全湖每升水样含浮游植物细胞密度年均值为614×105个,并且以蓝藻占绝对优势,年均值为423×105个/L,绿藻、硅藻次之,分别为97.3×105个/L和77×105个/L。不同站位浮游植物种类组成的相似性指数值(sorensen 公式)在51.3-85.3范围。
相似文献
7.
Wei Hongfei Zhao Genhai Liu Hui Wang Han Ni Wenfeng Wang Peng Zheng Zhiming 《Bioprocess and biosystems engineering》2018,41(1):107-113
Bioprocess and Biosystems Engineering - Menaquinone homologs (MK-n), that is, MK-4, MK-5, and MK-6, can be produced by the fermentation of Flavobacterium. In this study, we proposed a simple and... 相似文献
8.
Hongxia Liu Peng Wang Yihua Hu Genhai Zhao Hui Liu Zhemin Li 《Biocontrol Science and Technology》2015,25(9):1011-1023
Methods for enhancing conidial yield and for harvesting pure fungal conidia of entomopathogenic fungi were investigated. Fermentation conditions (liquid-to-solid ratio, MgSO4·7H2O, incubation temperature, inoculum sizes, KNO3 and relative humidity) of Beauveria bassiana s.l. and Metarhizium anisopliae s.l. were optimised to increase the conidial yields that reached 11.2 mg/g and 24.5 mg/g, increases of 72% and 52% compared to the unoptimised yields of 6.5 mg/g and 16.1 mg/g, respectively. Three methods were compared for harvesting pure conidia of B. bassiana: dual cyclone equipment (DCE), sieving 200 and elution with 0.02% Tween-80 suspension. DCE performed the best, giving a conidial yield of 12.6 mg/g and 1.8 × 1010 conidia·g–1. To further enhance the harvest efficiency, response surface methodology combined with a Box–Behnken design was employed, and the conidial yield of B. bassiana reached 20.9 mg/g, a total increase of 221% compared to the original conditions. Under these optimised harvest parameters, the conidial yield of M. anisopliae rose to 42.2 mg/g, an increase of 162%. The conidia of B. bassiana and M. anisopliae harvested in this way were pure, with no mycelial fragments or substrate visible in microscopic images. 相似文献
9.
Hui Liu Peng Wang Guohong Gong Li Wang Genhai Zhao Zhiming Zheng 《Biotechnology letters》2013,35(3):423-429
Chitin synthases, that catalyze the formation of chitin the major component of cell walls in most filamentous fungi, play crucial roles in the growth and morphogenesis. To investigate the roles of chitin synthase in Penicillium chrysogenum, we developed an RNAi system to silence the class III chitin synthase gene chs4. After transformation, mutants had a slow growth rate and shorter but highly branched hyphae. All transformants either were unable to form conidia or could form only a few. Changes in chs4 expression could lead to a completely different morphology and eventually cause distinct penicillin yields. In particular, the yield of one transformant was 41 % higher than that of the original strain. 相似文献
10.
Size-fractionated biomass and productivity of phytoplankton and particulate organic carbon in the southern ocean 总被引:3,自引:0,他引:3
During the austral summer of 1989/1990, surface samples were obtained of size-fractionated biomass, and the productivity of
phytoplankton, its cell abundance, the composition of the dominant species, the concentration of particulate organic carbon
(POC) and the related environmental surface parameters were measured in a large-scale survey primarily of the Atlantic and
Indian Sectors. The results showed that the southern atlantic sector is the most fertile; chlorophylla (Chla) concentration averaged over 2 μg l−1, average cell abundance was about 41.0 × 103 cell l−1, and average POC concentration was also the highest (>100 μg l−1), but was lower in the Drake Passage and the southern Indian sector. The results for size-fractionated Chla showed that netplankton (>20 μm) in the South Atlantic Ocean, having abundant nutrients, accounted for the highest proportion
(average 65%) of biomass. In the infertile South Indian Ocean, picoplankton (<2 μm) accounted for the highest proportion,
averaging 47%. The results for size-fractionated productivity showed that the contribution of picoplankton to total productivity
was the largest in the South Atlantic Ocean and Drake Passage, those of nanoplankton (2–20 μm) and netplankton being about
equal. The relatively high photosynthesis assimilation number of picoplankton demonstrates their importance in the marine
ecosystems of Antarctic water. In comparison with the Antarctic water, the subantarctic and subtropical waters are infertile. 相似文献