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Porcine growth hormone (pGH) is a class of peptide hormones secreted from the pituitary gland, which can significantly improve growth and feed utilization of pigs. However, it is unstable and volatile in vitro. It needs to be encapsulated in liposomes when feeding livestock, whose high cost greatly limits its application in pig industry. Therefore we attempted to express pGH as intracellular soluble protein in Pichia pastoris and feed these yeasts with partial wall-breaking for swine, which could release directly pGH in intestine tract in case of being degraded in intestinal tract with low cost. In order to improve the intracellular soluble expression of pGH protein in Pichia pastoris and stability in vitro, we optimized the pGH gene, and screened molecular chaperones from E. coli and Pichia pastoris respectively for co-expressing with pGH. In addition, we had also explored conditions of mechanical crushing and fermentation. The results showed that the expression of intracellular soluble pGH protein was significantly increased after gene optimized and co-expressed with Ssa1-Sis1 chaperone from Pichia pastoris. Meanwhile, the optimal conditions of partial wall-breaking and fermentation of Pichia pastoris were confirmed, the data showed that the intracellular expression of the optimized pGH protein coexpressed with Ssa1-Sis1 could reach 340 mg/L with optimal conditions of partial wall-breaking and fermentation. Animal experiments verified that the optimized pGH protein co-expression with Ssa1-Sis1 had the best promoting effects on the growth of piglets. Our study demonstrated that Ssa1-Sis1 could enhance the intracellular soluble expression of pGH protein in Pichia pastoris and that partial wall-breaking of yeast could prevent pGH from degradation in vitro, release targetedly in the intestine and play its biological function effectively. Our study could provide a new idea to cut the cost effectively, establishing a theoretical basis for the clinic application of unstable substances in vitro.

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Ciprofloxacin (CIP), as a representative broad-spectrum antibiotic, poses a major threat to human health and the ecological environment as a result of its abuse and emissions. In this study, a highly active Mn2+-oxidizing bacterium, Pseudomonas sp. CCTCC M2014168, was induced to form micro-/nanostructured biogenic Mn oxide (BMO) aggregates through continuous culturing with 1 mmoL−1 Mn2+. Following the characterization of Mn4+ oxides and the micro-/nanostructures by scanning electron microscopy, high-resolution transmission electron microscopy and X-ray diffraction assays, the BMO composites were subjected to CIP degradation and detoxification in laboratory trials. High-performance liquid chromatograph (HPLC) analysis identified that the BMO composites were capable of completely degrading CIP, and HPLC with a mass spectrometer (LC/MS) assays identified three intermediates in the degradation pathway. The reaction temperature, pH and initial ciprofloxacin concentration substantially affected the degradation efficiency of CIP to a certain extent, and the metal ions Mg2+, Cu2+, Ni2+ and Co2+ exerted significant inhibitory effects on CIP degradation. A toxicity test of the degradation products showed that CIP was completely detoxified by degradation. Moreover, the prepared BMO composite exhibited a high capacity for repeated degradation and good performance in continuous degradation cycles, as well as a high capacity to degrade CIP in real natural water.