Production of controlled molecular weight hyaluronic acid by glucostat strategy using recombinant Lactococcus lactis cultures

The expression of HIV-1 tat in Lactococcus lactis

Efficient expression of functional proteins in heterologous hosts has become the pivotal focus of modern biotechnology and biomedical research. To this end, multiple alternatives to E. coli are being explored for recombinant protein expression. L. lactis, being a gram-positive organism, circumvents the need for an endotoxin removal step during protein purification. We report here the optimisation of the expression of HIV-1 Tat, a notoriously difficult protein, in Lactococcus lactis system. We evaluated five different promoters in two different Lactococcus lactis strains and examined the effect of pH, glucose, and induction time on the yield and purity of Tat. Finally, the recombinant Tat was functionally competent in transactivating the HIV-1 promoter in HLM-1 reporter cells. Our work provides a scaffold for future work on the expression of toxic proteins in Lactococcus lactis.

DNA-Aptamer-Based qPCR Using Light-Up Dyes for the Detection of Nucleic Acids

Quantitative polymerase chain reaction (qPCR) is widely used in detection of nucleic acids, but existing methods either lack sequence-specific detection or are costly because they use chemically modified DNA probes. In this work, we apply a DNA aptamer and light-up dye-based chemistry for qPCR for nucleic acid quantification. In contrast to the conventional qPCR, in our method, we observe an exponential decrease in fluorescence upon DNA amplification. The qPCR method we developed produced consistent Ct vs log10 (DNA amount) standard curves, which have a linearfit with R2 value > 0.99. This qPCR technique was validated by quantifying gene targets from Streptococcus zooepidemicus (SzhasB) and Mycobacterium tuberculosis (MtrpoB). We show that our strategy is able to successfully detect DNA at as low as 800 copies/μL. To the best of our knowledge, this is the first study demonstrating the application of light-up dyes and DNA aptamers in qPCR.

Polysaccharides-Naturally Occurring Immune Modulators

The prevention of disease and infection requires immune systems that operate effectively. This is accomplished by the elimination of infections and abnormal cells. Immune or biological therapy treats disease by either stimulating or inhibiting the immune system, dependent upon the circumstances. In plants, animals, and microbes, polysaccharides are abundant biomacromolecules. Due to the intricacy of their structure, polysaccharides may interact with and impact the immune response; hence, they play a crucial role in the treatment of several human illnesses. There is an urgent need for the identification of natural biomolecules that may prevent infection and treat chronic disease. This article addresses some of the naturally occurring polysaccharides of known therapeutic potential that have already been identified. This article also discusses extraction methods and immunological modulatory capabilities.

Microbial synthesis of glycosaminoglycans and their oligosaccharides

Compared with chemical synthesis and tissue extraction methods, microbial synthesis of glycosaminoglycans (GAGs) is attractive because of the advantages of eco-friendly processes, production safety, and sustainable development. However, boosting the efficiency of microbial cell factories, precisely regulating GAG molecular weights, and rationally controlling the sulfation degree of GAGs remain challenging. To address these issues, various strategies, including genetic, enzymatic, metabolic, and fermentation engineering, have been developed. In this review, we summarize the recent progress in the construction of efficient GAG-producing microbial cell factories, regulation of the molecular weight of GAGs, and modification of GAG chains. Moreover, future studies, remaining challenges, and potential solutions in this field are discussed.

Microbial Hyaluronic Acid Production: A Review

Microbial production of hyaluronic acid (HA) is an area of research that has been gaining attention in recent years due to the increasing demand for this biopolymer for several industrial applications. Hyaluronic acid is a linear, non-sulfated glycosaminoglycan that is widely distributed in nature and is mainly composed of repeating units of N-acetylglucosamine and glucuronic acid. It has a wide and unique range of properties such as viscoelasticity, lubrication, and hydration, which makes it an attractive material for several industrial applications such as cosmetics, pharmaceuticals, and medical devices. This review presents and discusses the available fermentation strategies to produce hyaluronic acid.

Curdlan production from cassava starch hydrolysates by Agrobacterium sp. DH-2

Curdlan is an edible microbial polysaccharide and can be used in food, biomedical and biomaterial fields. To reduce the cost of curdlan production, this study investigated the suitability of cassava starch hydrolysates as carbon source for curdlan production. Cassava starch was hydrolyzed into maltose syrup using β-amylase and pullulanase at various enzyme dosages, temperature, time and addition order of two enzymes. The maltose yield of 53.17% was achieved at starch loading 30% by simultaneous addition β-amylase 210 U/g starch and pullulanase 3 U/g starch at 60 °C for 9 h. Cassava starch hydrolysates were used as carbon source for curdlan production by Agrobacterium sp. DH-2. The curdlan production reached 28.4 g/L with the yield of 0.79 g/g consumed sugar and molecular weight of 1.26 × 10⁶ Da at 96 h with cassava starch hydrolysate at 90 g/L initial sugar concentration. Curdlan produced from cassava starch hydrolysates was characterized using FT-IR spectra and thermo gravimetric analysis. This work indicated that cassava starch was a potential renewable feedstock for curdlan production.

Indirect Pathway Metabolic Engineering Strategies for Enhanced Biosynthesis of Hyaluronic Acid in Engineered Corynebacterium glutamicum

Hyaluronic acid (HA) is composed of alternating d-glucuronic acid and N-acetyl-d-glucosamine, with excellent biocompatibility and water retention capacity. To achieve heterologous biosynthesis of HA, Corynebacterium glutamicum, a safe GRAS (generally recognized as safe) host, was utilized and metabolically engineered previously. In this work, to achieve further enhancement of HA yield, four strategies were proposed and performed separately first, i.e., (1) improvement of glucose uptake via iolR gene knockout, releasing the inhibition of transporter IolT1/IolT2 and glucokinases; (2) intensification of cardiolipin synthesis through overexpression of genes pgsA1/pgsA2/cls involved in cardiolipin synthesis; (3) duly expressed Vitreoscilla hemoglobin in genome, enhancing HA titer coupled with more ATP and improved NAD⁺/NADH (>7.5) ratio; and (4) identification of the importance of glutamine for HA synthesis through transcriptome analyses and then enhancement of the HA titer via its supplement. After that, we combined different strategies together to further increase the HA titer. As a result, one of the optimal recombinant strains, Cg-dR-CLS, yielded 32 g/L of HA at 60 h in a fed-batch culture, which was increased by 30% compared with that of the starting strain. This high value of HA titer will enable the industrial production of HA via the engineered C. glutamicum.

Collagen- and hyaluronic acid-based hydrogels and their biomedical applications

Hydrogels have been widely investigated in biomedical fields due to their similar physical and biochemical properties to the extracellular matrix (ECM). Collagen and hyaluronic acid (HA) are the main components of the ECM in many tissues. As a result, hydrogels prepared from collagen and HA hold inherent advantages in mimicking the structure and function of the native ECM. Numerous studies have focused on the development of collagen and HA hydrogels and their biomedical applications. In this extensive review, we provide a summary and analysis of the sources, features, and modifications of collagen and HA. Specifically, we highlight the fabrication, properties, and potential biomedical applications as well as promising commercialization of hydrogels based on these two natural polymers.

Genetic strategies for improving hyaluronic acid production in recombinant bacterial culture

Hyaluronic acid (HA) is a biopolymer of repeating units of glucuronic acid and N-acetylglucosamine. Its market was valued at USD 8.9 billion in 2019. Traditionally, HA has been obtained from rooster comb-like animal tissues and fermentative cultures of attenuated pathogenic streptococci. Various attempts have been made to engineer a safe micro-organism for HA synthesis; however, the HA titres obtained from these attempts are in general still lower than those achieved by natural, pathogenic producers. In this scenario, ways to increase HA molecule length and titres in already constructed strains are gaining attention in the last years, but no recent publication has reviewed the main genetic strategies applied to improve HA production on heterologous hosts. In light of that, we hereby compile the advances made in the engineering of micro-organisms to improve HA synthesis.

Current advances in the biosynthesis of hyaluronic acid with variable molecular weights

Hyaluronic acid (HA) is a naturally formed acidic mucopolysaccharide, with excellent moisturising properties and used widely in the medicine, cosmetics, and food industries. The industrial production of specific molecular weight HA has become imperative. Different biological activities and physiological functions of HA mainly depend on the degree of polymerisation. This article reviews the research status and development prospects of the green biosynthesis and molecular weight regulation of HA. There is an application-based prerequisite of specific molecular weight of HA that could be regulated either during the fermentation process or via a controlled HA degradation process. This work provides an important theoretical basis for the downstream efficient production of diversified HA, which will further accelerate the research applications of HA and provide a good scientific basis and method reference for the study of the molecular weight regulation of similar biopolymers.

Bioproduction of biomacromolecules for antiviral applications

The societal damage brought on by viral epidemics indicates that next-generation antiviral treatments must be developed and deployed. Biomacromolecules are a diverse class of compounds that can potentially exhibit potent antiviral activity. Their efficacy and mechanisms of action are dependent upon multiple structural factors, including molecular weight, degree and position of sulfation, and backbone stereochemistry. Extracting biomacromolecules from animals and plants for healthcare applications is undesirable, as these methods are unable to yield products with well-defined chemical structures. Modern advances utilizing recombinant microbes and metabolic pathway engineering can be a key step towards large-scale bioproduction of tailored biomacromolecules for targeted antiviral applications.

Evaluation of Ogataea (Hansenula) polymorpha for Hyaluronic Acid Production

Hyaluronic acid (HA) is a biopolymer formed by UDP-glucuronic acid and UDP-N-acetyl-glucosamine disaccharide units linked by β-1,4 and β-1,3 glycosidic bonds. It is widely employed in medical and cosmetic procedures. HA is synthesized by hyaluronan synthase (HAS), which catalyzes the precursors’ ligation in the cytosol, elongates the polymer chain, and exports it to the extracellular space. Here, we engineer Ogataea (Hansenula) polymorpha for HA production by inserting the genes encoding UDP-glucose 6-dehydrogenase, for UDP-glucuronic acid production, and HAS. Two microbial HAS, from Streptococcus zooepidemicus (hasAs) and Pasteurella multocida (hasAp), were evaluated separately. Additionally, we assessed a genetic switch using integrases in O. polymorpha to uncouple HA production from growth. Four strains were constructed containing both has genes under the control of different promoters. In the strain containing the genetic switch, HA production was verified by a capsule-like layer around the cells by scanning electron microscopy in the first 24 h of cultivation. For the other strains, the HA was quantified only after 48 h and in an optimized medium, indicating that HA production in O. polymorpha is limited by cultivation conditions. Nevertheless, these results provide a proof-of-principle that O. polymorpha is a suitable host for HA production.

Eliminating the capsule-like layer to promote glucose uptake for hyaluronan production by engineered Corynebacterium glutamicum

Hyaluronan is widely used in cosmetics and pharmaceutics. Development of robust and safe cell factories and cultivation approaches to efficiently produce hyaluronan is of many interests. Here, we describe the metabolic engineering of Corynebacterium glutamicum and application of a fermentation strategy to manufacture hyaluronan with different molecular weights. C. glutamicum is engineered by combinatorial overexpression of type I hyaluronan synthase, enzymes of intermediate metabolic pathways and attenuation of extracellular polysaccharide biosynthesis. The engineered strain produces 34.2 g L⁻¹ hyaluronan in fed-batch cultures. We find secreted hyaluronan encapsulates C. glutamicum, changes its cell morphology and inhibits metabolism. Disruption of the encapsulation with leech hyaluronidase restores metabolism and leads to hyper hyaluronan productions of 74.1 g L⁻¹. Meanwhile, the molecular weight of hyaluronan is also highly tunable. These results demonstrate combinatorial optimization of cell factories and the extracellular environment is efficacious and likely applicable for the production of other biopolymers.

Bioproduction of hyaluronan needs increases in yield and greater diversity of the molecular weights. Here, the author increases hyaluronan production and diversifies the molecular weights through engineering the hyaluronan biosynthesis pathway and disruption of Corynebacterium glutamicum encapsulation caused by secreted hyaluronan.

Deciphering the role of dissolved oxygen and N-acetyl glucosamine in governing higher molecular weight hyaluronic acid synthesis in Streptococcus zooepidemicus cell factory

The present study is focused on systematic process and kinetic investigation of hyaluronic acid (HA) production strategy unraveling the role of dissolved oxygen (DO) and N-acetyl glucosamine (GlcNAc) towards the enhancement of HA titer and its molecular weight. Maintaining excess DO levels (10-40% DO) through DO-stat control and the substitution of GlcNAc at a range (5-20 g/L) with glucose (Glc) critically influenced HA production. DO-stat control strategy yielded a promising HA titer (2.4 g/L) at 40% DO concentration. Controlling DO level at 20% (DO-stat) was observed to be optimum resulting in a significant HA production (2.1 g/L) and its molecular weight ranging 0.98-1.45 MDa with a consistent polydispersity index (PDI) (1.57-1.69). Substitution of GlcNAc with Glc at different proportions explicitly addressed the metabolic trade-off between HA titer and its molecular weight. GlcNAc substitution positively influenced the molecular weight of HA. The highest HA molecular weight (2.53 MDa) of two-fold increase compared with glucose as sole carbon substrate and narrower PDI (1.35 ± 0.18) was achieved for the 10:20 (Glc:GlcNAc) proportion. A novice attempt on modeling the uptake of dual substrates (Glc and GlcNAc) by Streptococcus zooepidemicus for HA production was successfully accomplished using double Andrew's growth model and the kinetic parameters were estimated reliably.

Enhancement of acetyl-CoA by acetate co-utilization in recombinant Lactococcus lactis cultures enables the production of high molecular weight hyaluronic acid

The molecular weight of hyaluronic acid (HA) is a critical property which determines its usage in various biomedical applications. This study investigates the correlation between the availability of a critical cofactor, acetyl-CoA, the concentration of a limiting precursor, UDP-N-acetylglucosamine (UDP-GlcNAc), and the molecular weight of HA (MW_HA) produced by recombinant Lactococcus lactis MKG6 cultures. This strain expressed three heterologous HA-pathway genes obtained from the has operon of Streptococcus zooepidemicus in an ldh-mutant host strain, L. lactis NZ9020. A flux balance analysis, performed using the L. lactis genome-scale metabolic network, showed a positive correlation of acetyl-CoA flux with the UDP-GlcNAc flux and the experimental data on HA productivity. To increase the intracellular levels of acetyl-CoA, acetate was supplemented as a pulse feed in anaerobic batch cultures. However, acetate is effectively utilized only in the presence of glucose and exhaustion of glucose resulted in decreasing the final MW_HA (1.5 MDa). Co-supplementation of acetate resulted in enhancing the acetyl-CoA and UDP-GlcNAc levels as well as the MW_HA to 2.5 MDa. This logic was extended to fed-batch cultures, designed with a pH-based feedback control of glucose feeding and pulse acetate supplementation. When the glucose feed concentration was optimally adjusted to prevent glucose exhaustion or accumulation, the acetate utilization was found to be high, resulting in significantly enhanced levels of acetyl-CoA and UDP-GlcNAc as well as a MW_HA of 3.4 MDa, which was sustained at this value throughout the process. This study provides the possibility of commercially producing high MW_HA using recombinant L. lactis strains.