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A new balanced to balanced (BTB) filtering power divider (FPD) based on right triangle substrate integrated waveguide (SIW) cavity is proposed in this article. TE 120 -mode is used in four SIW right triangle cavities to realize required differential-mode (DM) transmission and common-mode (CM) suppression.Grounded resistors are loaded between DM output ports to obtain port-to-port isolation. The transmission zero out of the passband is generated by suppressing the TE 210 mode. A prototype BTB FPD operating at 14.91 GHz is designed, fabricated, and measured for verification. Good accordance between simulation and measurement can be observed.

Bacillus subtilis glutamine synthetase (GS) was highly expressed (about 86% of total protein) as soluble protein in Escherichia coli BL21(DE3) containing pET28a-glnA, which was induced by 0.4 mM IPTG in LB medium, and maximal theanine-forming activity of the recombinant GS induced in LB is 6.4 U/mg at a series concentration (0-100 mM) of Mn 2+ at optimal pH 7.5. In order to get GS with high theanine-forming activity, safety, and low cost for food and pharmaceutics industry, M9-A (details are described in ''Materials and methods'') and 0.1% (w/v) lactose were selected as culture medium and inducer respectively. Recombinant GS was also highly expressed (84% of total protein) and totally soluble in M9-A and the specific activity of the recombinant GS is 6.2 U/ mg which is approximate to that (6.4 U/mg) induced in LB in the presence of 10 mM Mn 2+ at optimal pH 7.5. The activity is markedly higher activated by Mn 2+ than that by other nine bivalent cations. Furthermore, M9-B (5 lM Mn 2+ was added into M9-A) was used to culture the recombinant strain and theanine-forming activity of the recombinant GS induced in M9-B was improved 20% (up to 7.6 U/mg). Finally, theanine production experiment coupled with yeast fermentation system was carried out in a 1.0 ml reaction system with 0.1 mg crude GS from M9-B or M9-A, and the yield of theanine were 15.3 and 13.1 g/L by paper chromatography and HPLC, respectively.

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