Production and secretion dynamics of prokaryotic Penicillin G acylase in Pichia pastoris

Cell factory-based milk protein biomanufacturing: Advances and perspectives

The increasing global population and protein demand cause global challenges for food supply. Fueled by significant developments in synthetic biology, microbial cell factories are constructed for the bioproduction of milk proteins, providing a promising approach for scalable and cost-effective production of alternative proteins. This review focused on the synthetic biology-based microbial cell factory construction for milk protein bioproduction. The composition, content, and functions of major milk proteins were first summarized, especially for caseins, α-lactalbumin, and β-lactoglobulin. An economic analysis was performed to determine whether cell factory-based milk protein production is economically viable for industrial production. Cell factory-based milk protein production is proved to be economically viable for industrial production. However, there still exist some challenges for cell factory-based milk protein biomanufacturing and application, including the inefficient production of milk proteins, insufficient investigation of protein functional property, and insufficient food safety evaluation. Constructing new high-efficiency genetic regulatory elements and genome editing tools, coexpression/overexpression of chaperone genes, and engineering protein secretion pathways and establishing a cost-effective protein purification method are possible ways to improve the production efficiency. Milk protein biomanufacturing is one of the promising approaches to acquiring alternative proteins in the future, which is of great importance for supporting cellular agriculture.

Proteomic analysis of Penicillin G acylases and resulting residues in semi-synthetic β-lactam antibiotics using liquid chromatography - tandem mass spectrometry

Penicillin G acylase (PGA), as a key enzyme, is increasingly used in the commercial production of semi-synthetic β-lactam antibiotics (SSBAs). With the substitution of conventional chemical synthesis by emerging bioconversion processes, more and more PGAs fermented from different types of strains such as Escherichia coli (E. coli, ATCC 11105), Achromobacter sp. CCM 4824 and Providencia rettgeri (ATCC 31052) have been used in this kind of enzymatic processes. As an intermediate reaction catalyst, PGA protein and its presence in the final products may cause a potential risk of human allergic reaction and bring challenges for both quality and process controls. To achieve qualitative and quantitative analysis of PGAs and their residues in SSBAs, a tryptic digestion coupled with liquid chromatography - tandem mass spectrometry (LC-MS/MS) method was developed and proposed because of advantages like high selectivity and sensitivity. A suitable filter aided sample preparation (FASP) method was also used to remove matrix interference and to enrich the target PGA retained in the ultrafiltration membrane for an efficient enzymatic hydrolysis and subsequent accurate MS detection. Finally, twelve batches of PGAs from eight companies were identified and categorized into two types of strains (E. coli and Achromobacter sp. CCM 4824) using proteomic analysis. In total nine batches of five types of SSBAs (amoxicillin, cephalexin, cefprozil, cefdinir and cefaclor) from eight manufacturers were selected for investigation. Trace levels of PGA residual proteins ranging from 0.01 to 0.44 ppm were detected in six batches of different SSBAs which were far lower than the safety limit of 35 ppm reported by DSM, a manufacturer with expertise in the production of SSBAs by enzymatic processes. The developed FASP with LC-MS/MS method is superior to traditional protein assays in terms of selectivity, sensitivity and accuracy. Moreover, it could provide in-depth analysis of amino acid sequences and signature peptides contributing to assignment of the strain sources of PGAs. This method could become a promising and powerful tool to monitor enzymatic process robustness and reliability of this kind of SSBAs manufacturing.

Exploitation of E. coli for the production of penicillin G amidase: a tool for the synthesis of semisynthetic β-lactam antibiotics

BACKGROUND

Penicillin G amidase/acylases from microbial sources is a unique enzyme that belongs to the N-terminal nucleophilic hydrolase structural superfamily. It catalyzes the selective hydrolysis of side chain amide/acyl bond of penicillins and cephalosporins whereas the labile amide/acyl bond in the β-lactam ring remains intact. This review summarizes the production aspects of PGA from various microbial sources at optimized conditions. The minimal yield from wild strains has been extensively improved using varying strain improvement techniques like recombination and mutagenesis; further applied for the subsequent synthesis of 6-aminopenicillanic acid, which is an intermediate molecule for synthesis of a wide range of novel β-lactam antibiotics. Immobilization of PGA has also been attempted to enhance the durability of enzyme for the industrial purposes.

SHORT CONCLUSION

The present review provides an emphasis on exploitation of E. coli to enhance the microbial production of PGA. The latest achievements in the production of recombinant enzymes have also been discussed. Besides E. coli, other potent microbial strains with PGA activity must be explored to enhance the yields.

Enzyme-catalyzed biodegradation of penicillin fermentation residues by β-lactamase OtLac from Ochrobactrum tritici

BACKGROUND

Biodegradation of antibiotics is a promising method for the large-scale removal of antibiotic residues in the environment. However, the enzyme that is involved in the biodegradation process is the key information to be revealed.

RESULTS

In this study, the beta-lactamase from Ochrobactrum tritici that mediates the biodegradation of penicillin V was identified and characterized. When searching the proteins of Ochrobactrum tritici, the β-lactamase (OtLac) was identified. OtLac consists of 347 amino acids, and predicted isoelectric point is 7.0. It is a class C β-lactamase according to BLAST analysis. The coding gene of OtLac was amplified from the genomic DNA of Ochrobactrum tritici. The OtLac was overexpressed in E. coli BL21 (DE3) and purified with Ni2+ column affinity chromatography. The biodegradation ability of penicillin V by OtLac was identified in an in vitro study and analyzed by HPLC. The optimal temperature for OtLac is 32 ℃ and the optimal pH is 7.0. Steady-state kinetics showed that OtLac was highly active against penicillin V with a Km value of 17.86 μM and a kcat value of 25.28 s-1 respectively.

CONCLUSIONS

OtLac demonstrated biodegradation activity towards penicillin V potassium, indicating that OtLac is expected to degrade penicillin V in the future.

Engineering of the unfolded protein response pathway in Pichia pastoris: enhancing production of secreted recombinant proteins

Folding and processing of proteins in the endoplasmic reticulum (ER) are major impediments in the production and secretion of proteins from Pichia pastoris (Komagataella sp.). Overexpression of recombinant genes can overwhelm the innate secretory machinery of the P. pastoris cell, and incorrectly folded proteins may accumulate inside the ER. To restore proper protein folding, the cell naturally triggers an unfolded protein response (UPR) pathway, which upregulates the expression of genes coding for chaperones and other folding-assisting proteins (e.g., Kar2p, Pdi1, Ero1p) via the transcription activator Hac1p. Unfolded/misfolded proteins that cannot be repaired are degraded via the ER-associated degradation (ERAD) pathway, which decreases productivity. Co-expression of selected UPR genes, along with the recombinant gene of interest, is a common approach to enhance the production of properly folded, secreted proteins. Such an approach, however, is not always successful and sometimes, protein productivity decreases because of an unbalanced UPR. This review summarizes successful chaperone co-expression strategies in P. pastoris that are specifically related to overproduction of foreign proteins and the UPR. In addition, it illustrates possible negative effects on the cell's physiology and productivity resulting from genetic engineering of the UPR pathway. We have focused on Pichia's potential for commercial production of valuable proteins and we aim to optimize molecular designs so that production strains can be tailored to suit a specific heterologous product. KEY POINTS: • Chaperones co-expressed with recombinant genes affect productivity in P. pastoris. • Enhanced UPR may impair strain physiology and promote protein degradation. • Gene copy number of the target gene and the chaperone determine the secretion rate.