Characterization of a Nattokinase from the Newly Isolated Bile Salt-Resistant Bacillus mojavensis LY-06

Enhanced Thermostability of Nattokinase by Computation-Based Rational Redesign of Flexible Regions

Nattokinase is a nutrient in healthy food natto that has the function of preventing and treating blood thrombus. However, its low thermostability and fibrinolytic activity limit its application in food and pharmaceuticals. In this study, we used bioinformatics analysis to identify two loops (loop10 and loop12) in the flexible region of nattokinase rAprY. Using this basis, we screened the G131S-S161T variant, which showed a 2.38-fold increase in half-life at 55 °C, and the M3 variant, which showed a 2.01-fold increase in activity, by using a thermostability prediction algorithm. Bioinformatics analysis revealed that the enhanced thermostability of the G131S-S161T variant was due to the increased rigidity and structural shrinkage of the overall structure. Additionally, the increased rigidity of the local region surrounding the active center and its mutated sites helps maintain its normal conformation in high-temperature environments. The increased catalytic activity of the M3 variant may be due to its more efficient substrate binding mechanism. We investigated strategies to improve the thermostability and fibrinolytic activity of nattokinase, and the resulting variants show promise for industrial production and application.

Probing the microbial diversity and probiotic candidates from Pakistani foods: isolation, characterization, and functional profiling

Probiotics represent beneficial living microorganisms that confer physiological, nutritional, and functional advantages to human health, holding significant potential for development of functional foods. This research aimed to isolate, identify, and characterize potential probiotic bacterial strains sourced from fermented and non-fermented foods from Pakistan. A total of 341 bacterial strains were isolated from diverse food samples (81) collected from various regions of Pakistan. Strains were identified using 16S rRNA gene sequencing and phylogenetic analysis. The identified strains belonged to genera Bacillus, Staphylococcus, Microbacterium, Shigella, Micrococcus, Enterococcus, Sporosarcina, Paenibacillus, Limosilactobacillus, Kosakonia, Dietzia, Leclercia, Lacticaseibacillus, Levilactobacillus, Kluyvera, Providencia, Enterobacter, Neisseria, Streptococcus, Acinetobacter, Corynebacterium, Pantoea, Mammaliicoccus, Pseudomonas, Burkholderia, and Alkalihalobacillus. Selected strains were chosen for probiotic assessment, employing existing literature as a guideline. Among these selections, six strains exhibited hemolytic activity, and seven strains displayed resistance to multiple antibiotics, prompting their exclusion from subsequent evaluations. The remaining strains demonstrated auto-aggregation capacities spanning 3.39-79.7%, and displayed coaggregation capabilities with reported food-borne pathogens. Furthermore, nine strains exhibited antimicrobial properties against food-borne pathogens. The assessment encompassed diverse characteristics such as cell surface hydrophobicity, survival rates under varying conditions, cholesterol reduction ability, casein digestion capability, and antioxidant activity. Phylogenomic analysis, digital-DNA DNA hybridization (digi-DDH), and average nucleotide identity (ANI) calculations unveiled novel species potentially belonging to the genera Sporosarcina and Dietzia. Based on these findings, we advocate for the consideration of Staphylococcus cohnii subsp. cohnii NCCP-2414, Lacticaseibacillus rhamnosus NCCP-2569 and Levilactobacillus brevis NCCP-2574 as prime probiotic candidates with the potential for integration into formulation of functional foods.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03903-6.

Improvement of the fibrinolytic activity, acid resistance and thermostability of nattokinase by surface charge engineering

Nattokinase is a promising thrombolytic drug due to its powerful fibrinolytic effect and few side effects. However, the low fibrinolytic activity and stability of nattokinase have limited its industrial production and oral application. In this study, the basic and neutral amino acid residues on the surface of recombinant nattokinase AprY from Bacillus mojavensis LY-06 (rAprY) were mutated to acidic amino acid residues by surface charge engineering strategy, and two variants K12D and N109D with 92.6 % and 8.4 % increased fibrinolytic activity were obtained. The R45E variant with enhanced acid stability and thermostability was also screened, its acid stability at pH 4 and t1/2 at 55 °C were 3.7-fold and 1.8-fold higher than that of wild type rAprY, respectively. Bioinformatics analysis showed that the increased activities of K12D and N109D variants were related to the increased flexibility of the region around their active centers. The increased rigidity of 97-103 amino acid residues around the active center of R45E may be the reason for its enhanced stability and reduced catalytic activity. The multipoint mutation K12D-N109D (M2)'s catalytic activity did not increase cumulatively, but its pH stability did. The nattokinase variants generated in this study have potential for industrial production and application.

Purification of fibrinolytic enzyme from Bacillus amyloliquefaciens GUTU06 and properties of the enzyme

A producing-fibrinolytic enzyme strain was isolated with high yield. The strain was identified as Bacillus amyloliquefaciens. B. amyloliquefaciens GUTU06 fibrinolytic enzyme was purified by acetone precipitation and reverse micelle. Acetone precipitation condition and reverse micelle condition were examined. Results showed that the total reverse micelle extraction efficiency was 64.49 % ± 1.6 %. The purification fold of the entire process reached 13.38. The optimum pH of purified enzyme is 5, and the optimum temperature is 45 °C. Fe3+ and K+ can enhance the fibrinolytic activity of the enzyme. Compared to commercial fibrinolytic enzymes such as urokinase and lumbrukinase, GUTU06 fibrinolytic enzymes have a lower pH optimal range and higher temperature stability. The molecular weight of the enzyme was approximately 28 kDa. Reverse micelle extraction with cetyl trimethylammonium bromide as a surfactant combined with acetone precipitation is suitable for separating and purifying fibrinolytic enzymes and a promising technique for obtaining active proteins.

Research progress on the fibrinolytic enzymes produced from traditional fermented foods

Cardiovascular diseases (CVDs) are a global health problem and leading cause of death worldwide. Thrombus formation, one of the CVDs, is essentially the formation of fibrin clots. The existing thrombolytic agents have the disadvantages of high price, short half-life, and high bleeding risk; hence, there is an urgent need to find the alternative thrombolytic agents. In recent years, traditional fermented foods have been widely investigated for their outstanding effects in the prevention and treatment of thrombus formation. In this review, we have focused on fibrinolytic enzymes produced by microorganisms during the fermentation of traditional fermented foods and their potential use for treating CVDs. First, we discussed about the sources of fibrinolytic enzymes and microbial strains that produce those enzymes followed by the optimization of fermentation process, purification, and physicochemical properties of fibrinolytic enzymes. Finally, we have summarized the thrombolytic effects of fibrinolytic enzymes in humans and mice. Fibrinolytic enzymes produced by microorganisms during the fermentation of traditional fermented foods not only lyse thrombi but also acts as anti-atherosclerotic, anti-hyperlipidemia, and neuroprotection agents. Therefore, fibrinolytic enzymes from traditional fermented foods have great potential for the prevention and treatment of CVDs.

Combined Computer-Aided Predictors to Improve the Thermostability of Nattokinase

Food-derived nattokinase has strong thrombolytic activity and few side effects. In the field of medicine, nattokinase has been developed as an adjuvant drug for the treatment of thrombosis, and nattokinase-rich beverages and health foods have also shown great potential in the field of food development. At present, the poor thermostability of nattokinase limits its industrial production and application. In this study, we used several thermostability-prediction algorithms to predict nattokinase from Bacillus mojavensis LY-06 (AprY), and screened two variants S33T and T174V with increased thermostability and fibrinolytic activity. The t1/2 of S33T and T174V were 8.87-fold and 2.51-fold those of the wild type AprY, respectively, and their enzyme activities were also increased (1.17-fold and 1.28-fold, respectively). Although the thermostability of N218L was increased by 2.7 times, the fibrinolytic activity of N218L was only 73.3% of that of wild type AprY. The multiple-point mutation results showed that S33T-N218L and S33T-T174V-N218L variants lost their activity, and the T174V-N218L variant did not show any significant change in catalytic performance, while S33T-T174V increased its thermostability and activity by 21.3% and 24.8%, respectively. Although the S33T-T174V variant did not show the additive effect of thermostability, it combined the excellent transient thermostability of S33T with the better thrombolytic activity of T174V. Bioinformatics analysis showed that the overall structure of S33T and T174V variants tended to be stable, while the structure of S33T-T174V variant was more flexible. Local structure analysis showed that the increased rigidity of the active center region (positions 64-75) and the key loop region (positions 129-130, 155-163, 187-192, 237-241, and 268-270) determined the increased thermostability of all variants. In addition, the enhanced flexibility of S33T-T174V variant in the Ca1 binding region (positions 1-4, 75-82) and the peripheral region of the catalytic pocket (positions 210-216) may account for the inability to superpose its thermostability. We explored the effective strategy to enhance the thermostability of nattokinase, and the resulting variants have potential industrial production and application.

Microbial nattokinase: from synthesis to potential application

Nattokinase (NK) is an alkaline serine protease with strong thrombolytic activity produced by Bacillus spp. or Pseudomonas spp. It is a potential therapeutic agent for thrombotic diseases because of its safety, economy, and lack of side effects. Herein, a comprehensive summary and analysis of the reports surrounding NK were presented, and the physical-chemical properties and producers of NK were first described. The process and mechanism of NK synthesis were summarized, but these are vague and not specific enough. Further results may be achieved if detection techniques such as multi-omics are used to explore the process of NK synthesis. The purification of NK has problems such as a complicated operation and low recovery rate, which were found when summarizing the techniques to improve the quality of finished products. If multiple simple and efficient precipitation methods and purification materials are combined to purify NK, it may be possible to solve the current challenges. Additionally, the application potential of NK in biomedicine was reviewed, but functional foods with NK are challenging for acceptance in daily life due to their unpleasant odor. Accordingly, multi-strain combination fermentation or food flavoring agents can improve the odor of fermented foods and increase people's acceptance of them. Finally, the possible future directions focused on NK studies were proposed and provided suggestions for subsequent researchers.

Production, purification, and functional properties of microbial fibrinolytic enzymes produced by microorganism obtained from soy-based fermented foods: developments and challenges

According to the World Health Organization, cardiovascular disease (CVD) has become a major cause of chronic illness around the globe. It has been reported that soy-based fermented food (SFF) is very effective in preventing thrombus (one of the most important contributing factors to CVD), which are mainly attributed to the bioactive substances, especially the fibrinolytic enzymes (FE) generated by microorganisms during the fermentation process of soybean food. This paper therefore mainly reviewed the microbial fibrinolytic enzymes (MFE) from SFF. We first discuss the use of microbial fermentation to produce FE, with an emphasis on the strains involved. The production, purification, physicochemical properties, structure-functional attributes, functional properties and possible application of MFE from SFF are then discussed. Finally, current limitations and future perspectives for the production, purification, and the practical application of MFE are discussed. MFE from SFF pose multiple health benefits, including thrombolysis, antihypertension, anti-inflammatory, anti-hyperlipidemia, anticancer, neuroprotective, antiviral and other activities. Therefore, they exhibit great potential for functional foods and nutraceutical applications, especially foods with CVDs prevention potential.