Lycopene is a highly valued carotenoid with wide applications in various industries. The market demand for lycopene promotes research in metabolic engineering of heterologous hosts for lycopene. In this study, Pichia pastoris strain GS115 was genetically engineered to produce lycopene by integrating the heterologous lycopene biosynthesis genes from Corynebacterium glutamicum ATCC13032. The resulting strain, L1, produced 0.115 mg/g cell dry weight (DCW) lycopene. Through optimization by promoter selection, improving the precursor supply and expanding the Geranylgeranyl diphosphate (GGPP) pool, ultimately, the lycopene yield of the final optimal strain was 6.146 mg/g DCW with shake flask fermentation and 9.319 mg/g DCW (0.714 g/L) in a 3 L fermenter. The lycopene yield in this study is the highest yield of lycopene in P. pastoris reported to date, which demonstrated the potential of P. pastoris in lycopene synthesis and as a candidate host organism for the synthesis of other high value-added terpenoids.

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The halophilic bacterial strain PT-20, isolated from saline alkali soil samples and identified as a member of the genus Oceanobacillus, exhibited a robust ability to degrade phenol under high salt conditions. It was determined that strain PT-20 was capable of degrading 1000 mg L À1 phenol completely in the presence of 10% NaCl within 120 h. Under the optimal degradation conditions, pH 8.0, 3% NaCl and 30 C, 1000 mg L À1 phenol could be completely degraded in 48 h. Interestingly, the biodegradation rate of phenol was dramatically improved in the presence of glycine betaine. When glycine betaine was added, the time required to degrade 1000 mg L À1 phenol completely was significantly reduced from 120 h to 72 h, and the corresponding average degradation rate increased from 8.43 to 14.28 mg L À1 h À1 with 10% NaCl. Furthermore, transcriptome analysis was performed to investigate the effects of phenol and glycine betaine on the transcriptional levels of strain PT-20. The results indicated that the addition of glycine betaine enhanced the resistance of cells to phenol, increased the growth rate of strain PT-20 and upregulated the expression of related enzyme genes. In addition, the results of enzyme activity assays indicated that strain PT-20 degraded phenol mainly through a meta-fission pathway.

Fermentation process was applied to relieve the substrate transport-limitation of P. pastoris whole-cell biocatalysts, which was much simpler, more energy-saving and greener than c traditional permeabilizing reagent and ultrasonication treatment.

The large-scale fermentation of Pichia pastoris for recombinant protein production would be time consuming and produce a large amount of waste yeast. Here we introduce a novel semi-continuous fermentation process for P. pastoris GS115 that can separate vitality cells from broth and recycle the cells to produce high-secretory recombinant pectate lyase. It is based on differences in cell sedimentation coefficients with the formation of salt bridges between metal ions and various cell states. Compared to batch-fed cultivation and general semi-continuous culture, the novel process has significant advantages, such as consuming fewer resources, taking less time, and producing less waste yeast. Sedimentation with the addition of Fe3+ metal ions consumed 14.8 ± 0.0% glycerol, 97.8 ± 1.3% methanol, 55.0 ± 0.9 inorganic salts, 81.5 ± 0.0% time cost, and 77.0 ± 0.1% waste yeast versus batch-fed cultivation to produce an equal amount of protein; in addition, the cost of solid–liquid separation was lower for cells in the collected fermentation broth. The process is economically and environmentally efficient for producing recombinant proteins.