A novel process for phosphatidylserine production using a Pichia pastoris whole-cell biocatalyst with overexpression of phospholipase D from Streptomyces halstedii in a purely aqueous system

Rational design of phospholipase D to enhance thermostability and catalytic activity for efficient biocatalytic phosphatidylserine synthesis

Phospholipase D (PLD) is an essential enzyme for the enzymatic synthesis of phosphatidylserine (PS), but its widespread application is limited by its low stability and activity. Herein, a highly active and thermostable multi-mutant PLDM4 was obtained through a comprehensive strategy based on various computer-aided mutant design and systematic clustering analysis, extending its half-life from 3.7 to 89.8 min and enhancing its activity from 42.7 to 413.1 U/mL. The PLDM4 exhibited a higher PS synthesis efficiency in water-organic solvent system, reaching 119.1 g/L. The synthesis of PS within various edible oils was also achieved, producing PS-enriched edible oils (approximately 19.8 g/L) and creating opportunities to construct food grade PLD-mediated reaction system. These results highlight the proposed method providing an efficient tool and a promising mutant with enhanced thermal stability and activity, and expand the practical application of PLD in the food industry.

Immobilization of Phospholipase D on Fe3O4@SiO2-Graphene Oxide Nanocomposites: A Strategy to Improve Catalytic Stability and Reusability in the Efficient Production of Phosphatidylserine

Phospholipase D (PLD) plays a pivotal role in the biosynthesis of phosphatidylserine (PS), but its practical application is constrained by limitations in stability and reusability. In this study, we successfully fabricated the Fe3O4@SiO2-graphene oxide (GO) nanocomposite by chemical binding of Fe3O4@SiO2 and GO. Subsequently, PLD was immobilized onto the nanocomposite via physical adsorption, with the aim of enhancing catalytic stability, reducing mass transfer resistance, and improving reusability. Under optimal conditions, the immobilization efficiency reached 84.4%, with a PLD loading capacity of 111.4 mg/gsupport. The optimal pH for PS production by immobilized PLD shifted from 6.0 to 6.5, while the optimal temperature increased from 45 °C to 50 °C. Notably, the immobilized PLD demonstrated a shorter reaction time and a higher PS yield, achieving a 95.4% yield within 90 min, compared to the free PLD (78.1% yield within 150 min), representing a 1.04-fold improvement in production efficiency. Furthermore, the immobilized PLD exhibited outstanding storage stability and thermal stability, along with remarkable reusability. Even after being reused for 10 cycles, the PS yield still stays as high as 78.3%. These findings strongly suggest that the Fe3O4@SiO2-GO immobilized PLD has the potential for the efficient production of PS.

Phosphatidylserine: A comprehensive overview of synthesis, metabolism, and nutrition

Phosphatidylserine (PtdS) is classified as a glycerophospholipid and a primary anionic phospholipid and is particularly abundant in the inner leaflet of the plasma membrane in neural tissues. It is synthesized from phosphatidylcholine or phosphatidylethanolamine by exchanging the base head group with serine, and this reaction is catalyzed by PtdS synthase-1 and PtdS synthase-2 located in the endoplasmic reticulum. PtdS exposure on the outside surface of the cell is essential for eliminating apoptotic cells and initiating the blood clotting cascade. It is also a precursor of phosphatidylethanolamine, produced by PtdS decarboxylase in bacteria, yeast, and mammalian cells. Furthermore, PtdS acts as a cofactor for several necessary enzymes that participate in signaling pathways. Beyond these functions, several studies indicate that PtdS plays a role in various cerebral functions, including activating membrane signaling pathways, neuroinflammation, neurotransmission, and synaptic refinement associated with the central nervous system (CNS). This review discusses the occurrence of PtdS in nature and biosynthesis via enzymes and genes in plants, yeast, prokaryotes, mammalian cells, and the brain, and enzymatic synthesis through phospholipase D (PLD). Furthermore, we discuss metabolism, its role in the CNS, the fortification of foods, and supplementation for improving some memory functions, the results of which remain unclear. PtdS can be a potentially beneficial addition to foods for kids, seniors, athletes, and others, especially with the rising consumer trend favoring functional foods over conventional pills and capsules. Clinical studies have shown that PtdS is safe and well tolerated by patients.

Biodegradation of bisphenol A by a Pichia pastoris whole-cell biocatalyst with overexpression of laccase from Bacillus pumilus and investigation of its potential degradation pathways

Bisphenol A (BPA), an endocrine disrupter with estrogen activity, can infiltrate animal and human bodies through the food chain. Enzymatic degradation of BPA holds promise as an environmentally friendly approach while it is limited due to lower stability and recycling challenges. In this study, laccase from Bacillus pumilus TCCC 11568 was expressed in Pichia pastoris (fLAC). The optimal catalytic conditions for fLAC were at pH 6.0 and 80 °C, with a half-life T1/2 of 120 min at 70 °C. fLAC achieved a 46 % degradation rate of BPA, and possible degradation pathways were proposed based on identified products and reported intermediates of BPA degradation. To improve its stability and degradation capacity, a whole-cell biocatalyst (WCB) was developed by displaying LAC (dLAC) on the surface of P. pastoris GS115. The functionally displayed LAC demonstrated enhanced thermostability and pH stability along with an improved BPA degradation ability, achieving a 91 % degradation rate. Additionally, dLAC maintained a degradation rate of over 50 % after the fourth successive cycles. This work provides a powerful catalyst for degrading BPA, which might decontaminate endocrine disruptor-contaminated water through nine possible pathways.

Whole-Cell Display of Phospholipase D in Escherichia coli for High-Efficiency Extracellular Phosphatidylserine Production

Phospholipids are widely utilized in various industries, including food, medicine, and cosmetics, due to their unique chemical properties and healthcare benefits. Phospholipase D (PLD) plays a crucial role in the biotransformation of phospholipids. Here, we have constructed a super-folder green fluorescent protein (sfGFP)-based phospholipase D (PLD) expression and surface-display system in Escherichia coli, enabling the surface display of sfGFP-PLDr34 on the bacteria. The displayed sfGFP-PLDr34 showed maximum enzymatic activity at pH 5.0 and 45 °C. The optimum Ca2+ concentrations for the transphosphatidylation activity and hydrolysis activity are 100 mM and 10 mM, respectively. The use of displayed sfGFP-PLDr34 for the conversion of phosphatidylcholine (PC) and L-serine to phosphatidylserine (PS) showed that nearly all the PC was converted into PS at the optimum conditions. The displayed enzyme can be reused for up to three rounds while still producing detectable levels of PS. Thus, Escherichia coli/sfGFP-PLD shows potential for the feasible industrial-scale production of PS. Moreover, this system is particularly valuable for quickly screening higher-activity PLDs. The fluorescence of sfGFP can indicate the expression level of the fused PLD and changes that occur during reuse.

Efficient secretory expression of phospholipase D for the high-yield production of phosphatidylserine and phospholipid derivates from soybean lecithin

Phospholipase D (PLD) is an essential biocatalyst for the biological production of phosphatidylserine and phospholipid modification. However, the efficient heterologous expression of PLD is limited by its cell toxicity. In this study, a PLD was secretory expressed efficiently in Bacillus subtilis with an activity around 100 U/mL. A secretory expression system containing the signal peptide SP_EstA and the dual-promoter P_HpaII-SrfA was established, and the extracellular PLD activity further reached 119.22 U/mL through scale-up fermentation, 191.30-fold higher than that of the control. Under optimum reaction conditions, a 61.61% conversion ratio and 21.07 g/L of phosphatidylserine production were achieved. Finally, the synthesis system of PL derivates was established, which could efficiently synthesis novel PL derivates. The results highlight that the secretory expression system constructed in this study provides a promising PLD producing strain in industrial application, and laid the foundation for the biosynthesis of phosphatidylserine and other PL derivates. As far as we know, this work reports the highest level of extracellular PLD expression to date and the enzymatic production of several PL derivates for the first time.

Immunomodulatory effects of vinegar-egg juice: Potential pharmacological effects of a traditional Chinese food remedy?

Thousands of years of historical practice have proven that the ancient Chinese food, vinegar-egg juice, has immune-boosting effects with the presence of many nutritional factors. However, its mechanism of action in the body remains unclear. In this research project, vinegar-egg juice was chosen to analyze its immune-enhancing effects on mice. The immune enhancing effects of egg, vinegar and vinegar egg juice on lymphocytes of mouse spleen were compared. The effects on immune function of mice were analyzed by studying the organ index, natural killer(NK) cell activity, lymphocyte transformation function and cytokine changes in immune organs after treatment with vinegar-egg juice. The mechanism of immune enhancement was speculated by analyzing the changes of total IKKα/β/IκBα/NF-κB and its phosphorylated protein kinase by Western blot. Experiments have shown that vinegar and eggs have less immune regulation than vinegar-egg juice. Vinegar-egg juice can regulate the cellular and humoral immunity of spleen lymphocytes, increase the phosphorylated kinases of IKKα/β, reduce the total protein expression of IκBα, and activate the signaling pathway of IKK/IκB/NF-κB. In addition, compared with the control group, vinegar-egg juice reduced the Firmicutes/Bacteroidetes ratio and increased the relative abundance of beneficial bacteria. Furthermore, vinegar-egg juice can raise phosphatidylserine (PS) and serotonin (5-HT) levels in the body. The results showed that the vinegar-egg juice had obvious immunomodulatory activity. It was speculated that the intake of vinegar-egg juice can increase the activity of NK cells, T lymphocytes and B lymphocytes by increasing 5-HT levels, ultimately enhancing the body's immune function. PRACTICAL APPLICATIONS: In this work, we evaluated the immune regulation of vinegar, egg and vinegar-egg juice in mice. In addition, we investigated the effects of vinegar-egg juice on gut microbiota. And combined with the composition of the vinegar-egg juice, it was found that the intake of vinegar-egg juice could increase the activity of NK cells, T lymphocytes and B lymphocytes by increasing 5-HT levels, ultimately enhancing the body's immune function. On the basis of the results of this study, we recommend vinegar-egg juice can be a potential health food to resist the epidemic and improve autoimmunity in special times of the novel coronavirus outbreak.

Remodeling Bacillus amyloliquefaciens Cell Wall Rigidity to Reduce Cell Lysis and Increase the Yield of Heterologous Proteins

Bacillus amyloliquefaciens has great potential as a host for heterologous protein production, but its severe autolytic behavior has precluded its industrial application to date. Because d,l-endopeptidase activity-guided cell wall rigidity is considered essential for autolysis resistance, we investigated the effects of d,l-endopeptidase genes lytE, lytF, cwlO, and cwlS play on the growth, lysis, and morphology remodeling of B. amyloliquefaciens strain TCCC11018. Individual and combinatorial deletion of lytE, lytF, and cwlS enhanced the cell growth and delayed cell lysis. For the best mutant with the lytF and cwlS double deletion, the viable cell number at 24 h increased by 11.90% and the cell wall thickness at 6 h increased by 25.87%. Transcriptomic and proteomic analyses indicated that the improvement was caused by enhanced peptidoglycan synthesis. With the lytF and cwlS double deletion, the extracellular green fluorescent protein and phospholipase D expression levels increased by 113 and 55.89%, respectively. This work broadens our understanding of the relationship between d,l-endopeptidases and B. amyloliquefaciens cell characteristics, which provides an effective strategy to improve the heterologous protein expression in B. amyloliquefaciens-based cell factories.

Biotechnological application of Streptomyces for the production of clinical drugs and other bioactive molecules

Streptomyces is one of the most relevant genera in biotechnology, and its rich secondary metabolism is responsible for the biosynthesis of a plethora of bioactive compounds, including several clinically relevant drugs. The use of Streptomyces species for the manufacture of natural products has been established for more than half a century; however, the tremendous advances observed in recent years in genetic engineering and molecular biology have revolutionised the optimisation of Streptomyces as cell factories and drastically expanded the biotechnological potential of these bacteria. Here, we illustrate the most exciting advances reported in the past few years, with a particular focus on the approaches significantly improving the biotechnological capacity of Streptomyces to produce clinical drugs and other valuable secondary metabolites.

Feedforward Control Combined with 4F Management on Postoperative Nursing Effects and Motor Function of Meniscus Sports Injuries: Based on a Prospective Case Analysis

Background

Because active functional training and management after knee cartilage sports injury is the key to treatment, care of patients after an operation with knee cartilage sports injury is critical.

Aims

To explore the effect of feedforward control combined with 4F management and after an operation nursing effect on patients with knee cartilage sports injury.

Materials and Methods

According to the random number table method, 100 patients with knee cartilage sports injury who were nursed in our hospital from June 2019 to June 2021 were selected as the research objects and divided into the control group and the instance of watching, noticing, or making a statement group with 50 cases in each group according to the different nursing order. Among them, the control group adopted 4F management combined with feedforward control nursing mode: all-weather, whole-process, whole-system, and all-around services for patients. On this basis, the instance of watching, noticing, or making a statement group cooperated with early healing/repairing training to compare fear and stress-related self-test of the two groups of patients after an operation. Knee function and quality of care are scored using tables.

Results

After nursing, the knee joint function score of the instance of watching, noticing, or making a statement group was higher than that of the control group, while the pain after the operation, sleep quality, fear, and stress self-rating scale scores were significantly lower than the control group (P < 0.05). The whole-process management, body position placement, risk evaluation, repairing training, all-weather service, whole-system management, and comprehensive service of the two groups of patients were very much improved. The nursing quality of watching, noticing, or making a statement group was significantly higher than the control group (P < 0.05).

Conclusion

Feedforward control combined with 4F management combined with early repairing training can effectively reduce the fear and stress after an operation pain and sleep quality of knee cartilage sports injury and help increase the recovery of knee combined function in a good way.

Phospholipids (PLs) know-how: exploring and exploiting phospholipase D for its industrial dissemination

Owing to their numerous nutritional and bioactive functions, phospholipids (PLs), which are major components of biological membranes in all living organisms, have been widely applied as nutraceuticals, food supplements, and cosmetic ingredients. To date, PLs are extracted solely from soybean or egg yolk, despite the diverse market demands and high cost, owing to a tedious and inefficient manufacturing process. A microbial-based manufacturing process, specifically phospholipase D (PLD)-based biocatalysis and biotransformation process for PLs, has the potential to address several challenges associated with the soybean- or egg yolk-based supply chain. However, poor enzyme properties and inefficient microbial expression systems for PLD limit their wide industrial dissemination. Therefore, sourcing new enzyme variants with improved properties and developing advanced PLD expression systems are important. In the present review, we systematically summarize recent achievements and trends in the discovery, their structural properties, catalytic mechanisms, expression strategies for enhancing PLD production, and its multiple applications in the context of PLs. This review is expected to assist researchers to understand current advances in this field and provide insights for further molecular engineering efforts toward PLD-mediated bioprocessing.

Established tools and emerging trends for the production of recombinant proteins and metabolites in Pichia pastoris

Besides bakers' yeast, the methylotrophic yeast Komagataella phaffii (also known as Pichia pastoris) has been developed into the most popular yeast cell factory for the production of heterologous proteins. Strong promoters, stable genetic constructs and a growing collection of freely available strains, tools and protocols have boosted this development equally as thorough genetic and cell biological characterization. This review provides an overview of state-of-the-art tools and techniques for working with P. pastoris, as well as guidelines for the production of recombinant proteins with a focus on small-scale production for biochemical studies and protein characterization. The growing applications of P. pastoris for in vivo biotransformation and metabolic pathway engineering for the production of bulk and specialty chemicals are highlighted as well.

Streptomycetes as platform for biotechnological production processes of drugs

Streptomyces is one of the most versatile genera for biotechnological applications, widely employed as platform in the production of drugs. Although streptomycetes have a complex life cycle and metabolism that would need multidisciplinary approaches, review papers have generally reported only studies on single aspects like the isolation of new strains and metabolites, morphology investigations, and genetic or metabolic studies. Besides, even if streptomycetes are extensively used in industry, very few review papers have focused their attention on the technical aspects of biotechnological processes of drug production and bioconversion and on the key parameters that have to be set up. This mini-review extensively illustrates the most innovative developments and progresses in biotechnological production and bioconversion processes of antibiotics, immunosuppressant, anticancer, steroidal drugs, and anthelmintic agents by streptomycetes, focusing on the process development aspects, describing the different approaches and technologies used in order to improve the production yields. The influence of nutrients and oxygen on streptomycetes metabolism, new fed-batch fermentation strategies, innovative precursor supplementation approaches, and specific bioreactor design as well as biotechnological strategies coupled with metabolic engineering and genetic tools for strain improvement is described. The use of whole, free, and immobilized cells on unusual supports was also reported for bioconversion processes of drugs. The most outstanding thirty investigations published in the last 8 years are here reported while future trends and perspectives of biotechnological research in the field have been illustrated. KEY POINTS: • Updated Streptomyces biotechnological processes for drug production are reported. • Innovative approaches for Streptomyces-based biotransformation of drugs are reviewed. • News about fermentation and genome systems to enhance secondary metabolite production.

Improving the catalytic performance of Pichia pastoris whole-cell biocatalysts by fermentation process

Whole-cell biocatalysts have a wide range of applications in many fields. However, the transport of substrates is tricky when applying whole-cell biocatalysts for industrial production. In this research, P. pastoris whole-cell biocatalysts were constructed for rebaudioside A synthesis. Sucrose synthase was expressed intracellularly while UDP-glycosyltransferase was displayed on the cell wall surface simultaneously. As an alternative method, a fermentation process is applied to relieve the substrate transport-limitation of P. pastoris whole-cell biocatalysts. This fermentation process was much simpler, more energy-saving, and greener than additional operating after collecting cells to improve the catalytic ability of whole-cell biocatalysts. Compared with the general fermentation process, the protein production capacity of cells did not decrease. Meanwhile, the activity of whole-cell biocatalysts was increased to 262%, which indicates that the permeability and space resistance were improved to relieve the transport-limitations. Furthermore, the induction time was reduced from 60 h to 36 h. The fermentation process offered significant advantages over traditional permeabilizing reagent treatment and ultrasonication treatment based on the high efficiency and simplicity.

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.

Efficient secretion expression of phospholipase D in Bacillus subtilis and its application in synthesis of phosphatidylserine by enzyme immobilization

Transphosphatidylation catalyzed by phospholipase D has gained increasing attention for producing phosphatidylserine (PS), which can be used in functional food and medicine. In this study, we investigated the effects of six signal peptides on the secretion of PLD (PLD_sa) from Streptomyces antibioticus TCCC 21059 in the food-grade GRAS bacterium Bacillus subtilis. It indicated that the optimal signal peptide DacB with an Ala-X-Ala sequence motif at the C-terminus showed the highest secretory expression ability, resulting in increased production of 2.84 U/mL PLD_sa. Then PLD_sa was immobilized on the epoxy-based carriers, and one of these carriers allowed PLD_sa loading of up to 2.7 mg/g. The immobilized PLD_sa was more stable over a wide range of pH value (4.5-7.5) and temperature (16 °C-60 °C) than free PLD_sa. Subsequently, the synthesis of PS from soybean phosphatidylcholine (PC) was carried out in purely aqueous solution using immobilized PLD_sa, leading to a high yield of 65%. The immobilized PLD_sa catalyst maintained a relative PS production of 60% after 5 recycles. Notably, the use of toxic solvent was completely eliminated in the whole process, which would be more profitable for the application of PS.

Enhancing the thermostability of phospholipase D from Streptomyces halstedii by directed evolution and elucidating the mechanism of a key amino acid residue using molecular dynamics simulation

To enhance the thermostability of phospholipase D (PLD), error-prone polymerase chain reaction method was used to create mutants of PLD (PLD_sh) from Streptomyces halstedii. One desirable mutant (S163F) with Ser to Phe substitution at position 163 was screened with high-throughput assay. S163F exhibited a 10 °C higher optimum temperature than wild-type (WT). Although WT exhibited almost no activity after incubating at 50 °C for 40 min, S163F still displayed 27% of its highest activity after incubating at 50 °C for 60 min. Furthermore, the half-life of S163F at 50 °C was 3.04-fold higher than that of WT. The analysis of molecular dynamics simulation suggested that the Ser163Phe mutation led to the formation of salt bridge between Lys300 and Glu314 and a stronger hydrophobic interaction of Phe163 with Pro341, Leu342, and Trp460, resulting in an increased structural rigidity and overall enhanced stability at high temperature. This study provides novel insights on PLD tolerance to high temperature by investigating the structure-activity relationship. In addition, it provides strong theoretical foundation and preliminary information on the engineering of PLD with improved characteristics to meet industrial demand.

Comparison of the expression of phospholipase D from Streptomyces halstedii in different hosts and its over-expression in Streptomyces lividans

Phospholipase D (PLD) proteins from Streptomyces species are useful biocatalysts for synthesizing phospholipid derivatives relevant for the pharmaceutical and food industry from low-cost phosphatidylcholine. The overexpression of PLD in a recombinant strain is necessary to achieve large-scale PLD production. In this study, we investigated the feasibility of expressing PLD from Streptomyces halstedii in different hosts. The enzymatic activity of PLD reached 69.12 U/mL in the homologous Streptomyces lividans host, which was around 50-fold higher than that in the original host. Meanwhile, in Escherichia coli and Pichia pastoris, PLD expression was poor and showed obvious toxicity to cells, which may have been one of the reasons for low levels of PLD observed in heterologous hosts. An induced (Ptip)/constitutive (PermE*) dual-promoter expression system in S. lividans was constructed, which could achieve constitutive expression with PLD enzymatic activity of 13.41 U/mL under non-induced conditions and yield the highest PLD enzymatic activity of 68.33 U/mL with 2 μg/mL thiostreptone. The concentration of the expensive inducer was significantly reduced to only 10% of that used in the original expression system without affecting the protein expression level, which provided a good foundation for subsequent industrial applications to reduce production costs.

Engineering a thermostable version of D-allulose 3-epimerase from Rhodopirellula baltica via site-directed mutagenesis based on B-factors analysis

D-allulose has received increasing attention due to its excellent physiological properties and commercial potential. The D-allulose 3-epimerase from Rhodopirellula baltica (RbDAEase) catalyzes the conversion of D-fructose to D-allulose. However, its poor thermostability has hampered its industrial application. Site-directed mutagenesis based on homologous structures in which the residuals on high flexible regions were substituted according to B-factors analysis, is an effective way to improve the thermostability and robustness of an enzyme. RbDAEase showed substrate specificity toward D-allulose with a K_m of 58.57 mM and k_cat of 1849.43 min^-1. It showed a melting temperature (T_m) of 45.7 °C and half-life (t_1/2) of 52.3 min at pH 8.0, 60 °C with 1 mM Mn²⁺. The Site-directed mutation L144 F strengthened the thermostability to a Δt_1/2 of 50.4 min, ΔTm of 12.6 °C, and ΔT₅₀⁶⁰ of 22 °C. It also improved the conversion rate to 28.6%. Structural analysis reveals that a new hydrophobic interaction was formed by the mutation. Thus, site-directed mutagenesis based on B-factors analysis would be an efficient strategy to enhance the thermostability of designed ketose 3-epimerases.