Re-circulative utilization of waste Pichia pastoris as efficient nitrogen source for enhancing butyric acid production

Anaerobically Digesting Hazardous Waste Pichia pastoris Associated with Butyric Acid Cleaner Production

Recombinant Pichia pastoris semisolid hazardous waste treatment is difficult and traditional solid waste treatment is not applicable. However, P. pastoris wastes have features of high density and enriched proteins/polysaccharides, which could supply nitrogen/carbon sources for butyric acid production. The waste P. pastoris was first treated using NaOH to form a waste yeast suspension, and then the suspension was mixed with glucose to obtain a starting medium containing 5.6 g DCW/L (dry cell weight) yeast to initiate butyrate fermentation. The suspension was intermediately supplemented to bring the total waste yeast concentration to 26.3 g DCW/L while continuously feeding the concentrated glucose solution. With the proposed strategy, butyrate concentration reached high levels of 51.0-54.0 g/L using Clostridium tyrobutyricum as the strain. Amino acids/oligosaccharides/SO₄ ^2- in the suspension, raw material costs, complicated pretreatment process, and butyric acid cleaner production could be effectively utilized, reduced, eliminated, and realized. However, the apparent waste P. pastoris reduction rate was only 49% per batch, thus a "tanks in-series type's repeated waste treating system" model was developed to theoretically explore the possibility of increasing the waste yeast reduction rate R. The simulation results indicated that when setting the treatment unit numbers at 4, waste solid concentration could decrease from 26.3 to 3.37 g DCW/L and the hazardous waste yeast reduction rate R would increase from 49 to 97%.

High butanol/acetone ratio featured ABE production using mixture of glucose and waste Pichia pastoris medium-based butyrate fermentation supernatant

In this study, butanol (ABE) fermentations were implemented in a 7 L anaerobic fermentor, by directly using the mixture of glucose solution with the corn/waste Pichia pastoris medium-based butyrate fermentation supernatants (BFS II) as the co-substrate, followed by consecutively feeding of the BFS and concentrated glucose solution. When compared with the major index of ABE fermentation using 150 g/L corn-based medium, butanol concentration could be maintained at high level of 12.7-12.8 g/L, butanol/acetone (B/A) largely increased from ~ 2.0 to 4.4-5.0, butanol yield on total carbon sources increased from 0.32-0.34 to 0.39-0.41 (mol base) with a higher butyrate/glucose consumption ratio of 37%-53%. Efficient utilization of butyrate, SO₄^2-, amino acids, oligosaccharides, etc. in BFS II and the intracellular NADH contributed to the ABE fermentation performance improvement. The proposed strategy could be considered as the second utilization of waste Pichia pastoris, which could save raw materials/operating costs, fully use the oligosaccharides/SO₄^2- in BFS II to relieve the working loads in downstream waste water treatment process, and increase fermentation products diversity/flexibility to deal with the varied marketing prices and requirements.

Green Process: Improved Semi-Continuous Fermentation of Pichia pastoris Based on the Principle of Vitality Cell Separation

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.