427165 Fed-Batch Cultivation for Induction Strategy When Induced with Lactose to Increase Production of Thermostable Phytase in Semi-Industrial Scale 16-L Bioreactor By E. coli BL21(DE3)

Wednesday, November 11, 2015: 10:00 AM
150D/E (Salt Palace Convention Center)
Nor Zalina Othman1, Roslinda Abd Malek1, Solleh Ramli2, Rajni Hatti-Kaul3, Mohamad Roji Sarmidi4 and Hesham EL Enshasy1, (1)Institute of Bioproduct Development, Universiti Teknologi Malaysia, Johor Bahru, Malaysia, (2)Institut of Bioproduct Development, Universiti Teknologi Malaysia, Johor Bahru, Malaysia, (3)Department of Biotechnology, Lund University, Lund, Sweden, (4)Institute Bioproduct Development, Universiti Teknologi Malaysia, Skudai, Malaysia

A recombinant Escherichia coli BL21 (DE3) which harbours the thermostable phytase gene from Bacillus sp.MD2 is used as the host cell. Lactose was used as an alternative inducer. Lactose can be metabolized as a carbon source and can contribute to increase the metabolic overflow which leads to acetic acid accumulation. The important of this study to observe the growth kinetics of E.coliBL21(DE3) when induced with lactose without addition of antibiotic in the semi-industrial scale 16-L bioreactor towards expression of phytase gene which is growth in the glycerol-minimal medium as the production medium.The present work underlines the great importance of production medium and induction strategy for efficient production of recombinant proteins towards excretion as extracellular phytase.Different modes of induction strategies were conducted: one-pulse, intermittent by feeding two pulse of lactose, constant feeding  and DO-stat concomitantly feeding with glycerol in the post-induction phase to determine the factors limiting the cell growth and distribution of phytase activity.It can be concluded that, addition of lactose as the only carbon source in the fermentation broth in the post induction phase was not only for the cell growth but also for heterologous protein expression by the host cells.  A combination of continuous glycerol feeding rate of 15 g L-1 h-1 and intermittent feeding of lactose without supplementation of amphicillin can maintain the specific growth rate of 0.11 h-1 with the maximum cell mass about 18.3 g L-1  due to dissolved oxygen limitation during cultivation. The plasmid was maintained stably in the culture throughout the fed-batch process without the use of an antibiotic. The ratio distribution of phytase activity between extracellular: periplasmic: cytoplasmic was 7.75:1.28:1. The extracellular phytase activity about 111.19 U mL-1 of the total phytase activity about 161.0 U mL-1 with productivity of almost 32,200.00 U L-1 h-1 after 5 hours of induction. In conclusion, the total phytase productivity is governed by the lactose feeding rate per unit biomass of host cells in the post-induction phase.

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See more of this Session: Advances in Food and Bioprocess Engineering
See more of this Group/Topical: Food, Pharmaceutical & Bioengineering Division