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首页> 外文会议>AIChE Annual Meeting >Bioprocess Strategies to Optimize Thermostable Phytase Production By Escherichia coli B121 (DE3) When Induced with Lactose
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Bioprocess Strategies to Optimize Thermostable Phytase Production By Escherichia coli B121 (DE3) When Induced with Lactose

机译：用乳糖诱导时，在大肠杆菌B121（DE3）中优化热稳态植酸酶生产的生物过程策略

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IPTGis used as a molecular mimic of allolactose, a lactose metabolite that triggers transcription of the lac operon. Unlike allolactose, the sulphur atom create a chemical bond which is non-hydrolyzed by the cell, preventing the cell from degradation by the host cells that makes the IPTG concentration remains constant (Fernandez-Castane et al., 2012). IPTG is however toxic and comparably expensive (Donovan et al., 1996). Nowadays, lactose has been considered as an alternative inducer in fermentation of recombinant E.coli. Since the product yields is compatible with IPTG as inducer however it depends on the strategy of induction to increase heterologus protein expression (Weng et al., 2006; Abdel-Hamid et al., 2014). Induction of promoter gene by lactose during foreign protein expression has a limiting step. It is clearly observed that IPTG can bind directly to the lac-repressor molecules and express the phytase protein after one hour of induction. However, the expression of phytase was delayed almost an hour compared induction with IPTG and the amount of lactose needed as inducer should be further optimized for cultivation in different scale (Tran et al., 2010). In case of lactose as inducer, a few steps are needed before induction process. This is due to the time needed by lactose to be transported into the cell by the present of lactose permease and processed to allolactose by β-galactosidase before binding to the repressor (Becker et al., 2012; Santillan et al., 2007). Furthermore, lactose can be metabolized as energy sources. Further catabolic activity of allolactose may produce glucose and galactose that can contribute to increase the metabolic overflow due to excess carbon sources during induction period (Santillan and Mackey, 2008). As a result of metabolite burden, the high concentrations of inducer that are often used in an effort to fully induce the lac promoter do not necessarily lead to maximal expression of a target protein. This is due to high residual lactose concentration in the broth led to accumulation of glucose by hydrolysis of excess lactose during post-induction phase (Lim et al., 2004). Therefore the objective of this study to optimize the induction strategy whenlactose as inducer with addition of additive for E. coli BL21 (DE3) which growth in glycerol minimal medium to increase productivity of phytase expression and leakage of expression protein from periplasmic space to outside of cell membrane in semi-scale bioreactor.
机译：IPTGIS用作异膜的分子模拟，乳糖代谢物触发LAC操纵子的转录。与类乳糖不同，硫原子产生由细胞不水解的化学键，防止细胞通过使IPTG浓度保持恒定的宿主细胞（Fernandez-Castane等，2012）。然而，IPTG毒性和相对昂贵（Donovan等，1996）。如今，乳糖被认为是重组大肠杆菌发酵中的替代诱导剂。由于产品产率与IPTG与诱导剂相容，因此它取决于诱导造成杂种蛋白表达的策略（Weng等人，2006; Abdel-Hamid等，2014）。在外来蛋白质表达期间乳糖诱导启动子基因具有限制步骤。清楚地观察到，IPTG可以直接与LaC-阻遏分子结合，并在诱导1小时后表达植酸酶蛋白。然而，植酸酶的表达几乎与IPTG的诱导相比诱导几乎延迟，并且应该进一步优化以不同规模的培养进一步优化所需的乳糖量（Tran等，2010）。在乳糖作为诱导物的情况下，在感应过程之前需要几步。这是由于乳糖通过乳糖允许释放的乳糖被输送到细胞中的时间，并通过β-半乳糖苷酶加工在与阻遏物结合之前（Becker等，2012; Santillan等，2007）。此外，乳糖可以作为能源代谢。异烯糖的进一步分解代谢活性可以产生葡萄糖和半乳糖，其可以有助于增加由于在诱导期间（Santillan和Mackey，2008）期间由于过量的碳源而增加代谢溢出。由于代谢物负担，通常用于完全诱导LAC启动子的高浓度的诱导剂不一定导致靶蛋白的最大表达。这是由于肉汤中的高残留乳糖浓度导致诱导后乳糖水解的葡萄糖积聚（LiM等，2004）。因此，本研究的目的是优化乳糖作为诱导剂的诱导策略，所述添加剂为大肠杆菌BL21（DE3）的添加剂，其在甘油最小培养基中生长，以提高植酸酶表达和从细胞外部的表达蛋白的表达蛋白泄漏的生产率。半级生物反应器中的膜。

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