Polygalacturonase (PG) production by Penicillium chrysogenum during solid-state fermentation was accompanied by decomposition of orange peels. A leaching procedure was developed through the selection of solvent, time and intensity of stirring. A maximum PG activity was observed after 48 h peel inoculation. Further cultivation decreased the enzyme activity significantly, up to 60% of the maximum PG activity. During fermentation, a rapid acidification of the solid medium which inhibited the pectinolytic enzyme, was observed. Buffering agents with different pH values and different ionic strengths were examined to identify the most suitable medium to avoid this problem. Buffer addition counteracted acidification and enhanced active protein production, which was observed for all of the applied pH values (6.5-8.0) of the buffering agent. The most satisfactory results were obtained when using the highest pH at 8.0. The protein content and PG activity increased from 3.5 mg/g and 1.09 U/g to 7.7 mg/g and 7.11 U/g during cultivation, with uncontrolled and pH-controlled medium, respectively. Measurements at wide pH and temperature ranges indicated an optimum for PG activity at pH 5.0 and 43°C; however, high thermal stability corresponded to lower temperatures, and a temperature of 37°C is thus recommended. Under these conditions, the operational stability was determined to be t1/2=570 h.

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The results contribute to the knowledge of cultivation parameters of E. coli K-12 strain BL21/pETSD10 on a bioreactor scale to overproduce an enzyme degrading β-1,3-glucans. The optimal values of protein concentration, specific activity and total glucanase activity as a function of aeration and stirring were evaluated by numerical analysis. The obtained values were validated as positive. The protein degrades some bonds in hemicellulose. Thus, the protein could be applied as one of the degrading components for hemicellulose.

In the structure of the novel zinc complex catena-poly[[diaqua(4-hydroxybenzohydrazide)zinc(II)]-μ-sulfato], [Zn(SO4)(C7H8N2O2)(H2O)2]n, the complex cations are linked by sulfate counter-ions into helical polymeric chains extending along the b axis. Each helix is stabilized by six intrachain hydrogen bonds involving stronger O-H...O (1.83-2.06 Å) and weaker N-H...O (2.20-2.49 Å) interactions. The Zn(II) atom displays a distorted octahedral geometry formed by the 4-hydroxybenzohydrazide ligand, two water molecules and two SO4(2-) ions, which is very similar to the metal-atom environment in a previously reported Co(II) complex [Zasłona, Drożdżewski & Kubiak (2010). J. Mol. Struct. 982, 1-8], especially the Zn-O and Zn-N bond lengths of 2.0453 (12)-2.1602 (9) and 2.1118 (12) Å, respectively.

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