Improving Expression of Bovine Lactoferrin N-Lobe by Promoter Optimization and Codon Engineering in Bacillus subtilis and Its Antibacterial Activity

Intestinal-specific oral delivery of lactoferrin with alginate-based composite and hybrid CaCO3-hydrogel beads

Sodium alginate hydrogel beads and sodium alginate/gellan gum composite hydrogel beads crosslinked by calcium chloride were prepared with different alginate concentrations (3-20 mg·mL-1). Additionally, a simple method for growing CaCO3in situ on the hydrogel to create novel inorganic-organic hybrid hydrogel beads was presented. FT-IR analysis revealed the involvement of hydrogen bonding and electrostatic interactions in bead formation. Swelling behavior in acidic conditions showed a maximum of 13 g/g for composite hydrogels and CaCO3-incorporated hybrid hydrogels. Lactoferrin encapsulation efficiency within these hydrogels ranged from 44.9 to 56.6%. In vitro release experiments demonstrated that these hydrogel beads withstand harsh gastric environments with <16% cumulative release of lactoferrin, achieving controlled release in intestinal surroundings. While composite sodium alginate/gellan gum beads exhibited slower gastrointestinal lactoferrin digestion, facile synthesis and pH responsiveness of CaCO3-incorporated hybrid hydrogel also provide new possibilities for future studies to construct a novel inorganic-organic synergetic system for intestinal-specific oral delivery.

New Horizons of Covalent Complex of Plant-Derived Recombinant Human Lactoferrin (OsrhLF) Combined with Different Polyphenols: Formation, Physicochemical Properties, and Gastrointestinal Fate

Four typical dietary polyphenols ((-)-epigallocatechin gallate (EGCG), quinic acid (QA), caffeic acid (CA), and ferulic acid (FA)) were covalently prepared with rice recombinant human lactoferrin (OsrhLF) and bovine lactoferrin (bLF), and their structure and physicochemical properties were investigated, different lycopene emulsions were made by ultrasonic emulsification to analyze gastrointestinal fate. The results indicated that the covalent modification polyphenols changed the secondary/tertiary structure of LF, significantly improving the surface hydrophilicity, thermal stability, and antioxidant activity of LF. Compared with the bLF group, the OsrhLF group was more hydrophilic and the thermal denaturation temperature of the OsrhLF-CA reached 104.4 °C. LF-polyphenol emulsions significantly enhanced the photochemical stability and bioavailability of lycopene and achieved effective encapsulation and protection of lycopene compared to free lycopene, and the OsrhLF-EGCG reached 58.94% lycopene bioavailability. In short, OsrhLF does not differ much from bLF in terms of physicochemical properties and has a strong potential in the field of dietary supplements.

Construction of Bacillus subtilis for efficient production of fengycin from xylose through CRISPR-Cas9

Fengycin is a multifunctional peptide antibiotic produced mainly by Bacillus species and the purpose of this research was to construct a Bacillus subtilis strain that can produce fengycin with the xylose as the substrate with CRSIPR-Cas9. Hence, at the beginning of this study, functional sfp and degQ were expressed in B. subtilis 168 strain to give the strain the ability to produce the fengycin with the titer of 71.21 mg/L. Subsequently, the native promoter PppsA of the cluster responsible for the fengycin synthesis was replaced by the Pveg promoter, resulting in a further 5.22-fold increase in fengycin titer. To confer xylose utilization capacity to B. subtilis, deletion of araR and constitutive overexpression of araE were performed, and the xylose consumption rate of the engineered strain BSUY06 reached 0.29 g/L/h, which is about 6.25-fold higher than that of the parent strain BSUY04-1. In the final phase of this study, the fermentation characteristics were observed and the initial xylose concentration was optimized. In this study, 40 g/L xylose was proved to be the most suitable initial concentration for growth and fengycin fermentation, which leading to a fengycin titer of 430.86 mg/L. This study demonstrated that lignocellulose, the clean and sustainable substrate with xylose as the second largest sugar, is a potential substrate for the production of fengycin.

Expressing recombinant human lactoferrin with antibacterial activity in Nicotiana benthamiana

Lactoferrin is a non-hematic iron-binding 80-kDa protein that exhibits antimicrobial activity. Higher plants function as "green bioreactors" for large-scale recombinant protein production. In this study, we transiently expressed recombinant human lactoferrin (rhLF) in Nicotiana benthamiana at a yield of approximately 40 µg g-1 fresh mass (gFM) using the Tsukuba system. Additionally, the expression level of rhLF increased when it was fused with KDEL, an endoplasmic reticulum retention motif. Purified plant-derived rhLF possesses antibacterial activity that inhibits the growth of Escherichia coli. These results indicated that rhLF containing antimicrobial activity can be produced in N. benthamiana using the Tsukuba system.

Combinatorial approach for improved production of whole-cell 3-aminopropionic acid in recombinant Bacillus megaterium: codon optimization, gene duplication and process optimization

In this study, we aimed to develop a Bacillus megaterium based whole-cell biocatalyst for the bio-production of 3-aminopropionic acid (3-APA). l-aspartate-α-decarboxylases (ADC) (EC: 4.1.1.11) from Escherichia coli, B. megaterium, Corynebacterium glutamicum, and Bacillus subtilis were expressed in B. megaterium. B. subtilis derived ADC (panD _Bs ) exhibited the highest ADC activity of 0.9 ± 0.02 U/mL in recombinant B. megaterium. Combination of codon optimization and gene duplication strategies resulted in 415.56% enhancement of ADC activity compared to panD _Bs . The culture growth conditions of B. megaterium (BMD-7) for 3-APA production were optimized as follows: inducer concentration, 0.5% (w/v); time of induction, 3 h; induction temperature, 37 °C and post-induction incubation time, 8 h. Improvement of the whole-cell biocatalytic process efficiency, was dealt by optimization of reaction temperature, reaction pH, metal ion additives and l-aspartic acid concentration. Shake flask level experiments yielded an enhanced 3-APA titer (16.18 ± 0.26 g/L) and a yield of 0.89 g/g under optimized conditions viz., 45 °C, pH 6.0 and 20 g/L of l-aspartic acid. This study demonstrates the potential of B. megaterium for 3-APA production and paves the scope for the development of 3-APA producing strains in near future.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02885-7.