Optimization of medium composition for production of chitin-glucan complex and mannose-containing polysaccharides by the yeast Komagataella pastoris

Understanding exopolysaccharide byproduct formation in Komagataella phaffii fermentation processes for recombinant protein production

BACKGROUND

Komagataella phaffii (Pichia pastoris) has emerged as a common and robust biotechnological platform organism, to produce recombinant proteins and other bioproducts of commercial interest. Key advantage of K. phaffii is the secretion of recombinant proteins, coupled with a low host protein secretion. This facilitates downstream processing, resulting in high purity of the target protein. However, a significant but often overlooked aspect is the presence of an unknown polysaccharide impurity in the supernatant. Surprisingly, this impurity has received limited attention in the literature, and its presence and quantification are rarely addressed.

RESULTS

This study aims to quantify this exopolysaccharide in high cell density recombinant protein production processes and identify its origin. In stirred tank fed-batch fermentations with a maximal cell dry weight of 155 g/L, the polysaccharide concentration in the supernatant can reach up to 8.7 g/L. This level is similar to the achievable target protein concentration. Importantly, the results demonstrate that exopolysaccharide production is independent of the substrate and the protein production process itself. Instead, it is directly correlated with biomass formation and proportional to cell dry weight. Cell lysis can confidently be ruled out as the source of this exopolysaccharide in the culture medium. Furthermore, the polysaccharide secretion can be linked to a mutation in the HOC1 gene, featured by all derivatives of strain NRRL Y-11430, leading to a characteristic thinner cell wall.

CONCLUSIONS

This research sheds light on a previously disregarded aspect of K. phaffii fermentations, emphasizing the importance of monitoring and addressing the exopolysaccharide impurity in biotechnological applications, independent of the recombinant protein produced.

Prospective bacterial and fungal sources of hyaluronic acid: A review

The unique biological and rheological properties make hyaluronic acid a sought-after material for medicine and cosmetology. Due to very high purity requirements for hyaluronic acid in medical applications, the profitability of streptococcal fermentation is reduced. Production of hyaluronic acid by recombinant systems is considered a promising alternative. Variations in combinations of expressed genes and fermentation conditions alter the yield and molecular weight of produced hyaluronic acid. This review is devoted to the current state of hyaluronic acid production by recombinant bacterial and fungal organisms.

Influence of Dissolved Oxygen Level on Chitin–Glucan Complex and Mannans Production by the Yeast Pichia pastoris

The yeast Pichia pastoris was cultivated under different dissolved oxygen (DO) levels (5, 15, 30 and 50% of the air saturation) to evaluate its impact on the production of the cell-wall polysaccharide chitin–glucan complex (CGC) and mannans. Decreasing the DO level from 50 to 15% had no significant impact on cell growth but substrate conversion into biomass was improved. Under such conditions, a mannans content in the biomass of 22 wt% was reached, while the CGC content in the biomass was improved from 15 to 18 wt%, confirming that the DO level also impacted on P. pastoris cell-wall composition. Overall mannans and CGC volumetric productivity values of 10.69 and 8.67 g/(L. day) were reached, respectively. On the other hand, the polymers’ composition was not significantly affected by decreasing the DO level. These results demonstrated that considerable energy savings can be made in the polysaccharide production process by reducing the DO level during cultivation of P. pastoris by improving the overall polymers’ productivity without altering their composition. This has impact on the polysaccharide production costs, which is of considerable relevance for process scale-up and products’ commercialization.

Modular development enables rapid design of media for alternative hosts

Developing media to sustain cell growth and production is an essential and ongoing activity in bioprocess development. Modifications to media can often address host or product‐specific challenges, such as low productivity or poor product quality. For other applications, systematic design of new media can facilitate the adoption of new industrially relevant alternative hosts. Despite manifold existing methods, common approaches for optimization often remain time and labor‐intensive. We present here a novel approach to conventional media blending that leverages stable, simple, concentrated stock solutions to enable rapid improvement of measurable phenotypes of interest. We applied this modular methodology to generate high‐performing media for two phenotypes of interest: biomass accumulation and heterologous protein production, using high‐throughput, milliliter‐scale batch fermentations of Pichia pastoris as a model system. In addition to these examples, we also created a flexible open‐source package for modular blending automation on a low‐cost liquid handling system to facilitate wide use of this method. Our modular blending method enables rapid, flexible media development, requiring minimal labor investment and prior knowledge of the host organism, and should enable developing improved media for other hosts and phenotypes of interest.

Green synthesis, characterization and biological evaluation of chitin glucan based zinc oxide nanoparticles and its curcumin conjugation

A well-organized, simplistic, and green route of chitin-glucan based zinc oxide nanoparticles (ChGC@ZnONPs) was synthesized using reducing and capping agent both in one as chitin-glucan complex (ChGC). Herein we report the bio-synthesis of Cur-ChGC@ZnONPs by the conjugation of curcumin (Cur) with ChGC@ZnONPs for the improvement of antioxidant and antibacterial activity. The synthesized nanoparticles were characterized by the UV-Visible (UV-Vis), particle size analyser, scanning electron microscope (SEM) with Energy-dispersive X-ray spectroscopy (EDX), Transmission electron microscope (TEM), X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR). Structure analysis, shape and crystalline size of nanomaterials were confirmed by scanning electron microscopy (SEM) and Transmission Electron Microscopy (TEM). The particle size analyser showed the particle size of nanomaterials and stability. Crystalline nature of both ChGC@ZnONPs and Cur-ChGC@ZnONPs were confirmed by the XRD spectra and FT-IR spectrum was used to examine the functional groups of nanomaterials. The antioxidant potential of conjugated nanomaterials were estimated using a DPPH free radical scavenging assay and ABTS^+⁎ assay. This analysis showed that after loading of Cur, antioxidant activity increases. The antibacterial assessment of conjugated nanomaterials were tested by different microorganisms and showed excellent antibacterial activity.

Improved S-adenosyl-l-methionine production in Saccharomyces cerevisiae using tofu yellow serofluid

S-adenosyl-l-methionine (SAM) has been attracting increasing attention because of its significance in the pharmaceutical industry; however, the high cost of this compound limits its application. Tofu yellow serofluid exhibits high nutritional value and is not costly; therefore, it can be utilized as a substrate in the fermentation industry. In the current study, Saccharomyces cerevisiae was cultured in the tofu yellow serofluid fermentation medium for the SAM biosynthesis. The optimum tofu yellow serofluid fermentation medium contained 70 g/L of glucose, 30 % of yellow serofluid, 20 g/L of l-methionine, and 2.5 g/L of ammonium citrate. Under these conditions, the optimum feeding strategy was established. The results revealed that the dry cell weight (DCW) reached 123.1 g/L, the maximum production of SAM was 16.14 g/L, the highest SAM productivity reached 1.048 g/L/h, and SAM content was determined at 131.1 mg/g DCW. Furthermore, addition of tofu yellow serofluid reduced the average cost of SAM by 31.9 % to compare with the culture process without addition of tofu yellow serofluid. Thus, the tofu yellow serofluid fermentation medium improved the production of SAM and significantly reduced the production costs.