Cell and Tissue Journal

Abstract Introduction: Concern over fossil energy costs and environmental deterioration, along with energy security, has created a strong motivation for research and development of routes to provide sustainable, renewable fuels. In recent years, the use of biomass to produce highly valued chemicals has attracted widespread attention. lignocellulosic biomass, as a promising renewable resource for biofuel production, has distinct advantages in terms of economic and environmental aspects. The conversion of renewable raw materials to hydrocarbon fuels is an attractive alternative to fossil fuels from an economic and environmental point of view. The production process of lignocellulosic biomass mainly consists of biomass accumulation, biomass decomposition, simple sugars, and conversion of sugars to biofuel. One of the crucial steps in the economic success of lignocellulosic biofuels depends on the inhibition of competitive metabolism in microorganisms to achieve high productivity. To date, a growing focus is on the use of S. cerevisiae and E. coli as cell lines. These two cellular factories have the benefits that are well known.

Aim: The organic compound D-1,2,4-Butanetriol is a valuable chemical with wide-ranging applications in various fields. The chemical synthesis routes for BT have many drawbacks. By genetically modifying microorganisms, the metabolic pathway for producing many substances, including BT, can be engineered. The organic compound D-1,2,4-butanediol (BT) is an important intermediate chemical widely used in fields such as pharmaceuticals, paper, polymer materials, and military applications. When D-xylose sugar is provided to the bacterium, it is first converted to an intermediate compound called xylonolactone. This compound itself slowly converts into xylonate through a non-enzymatic reaction. To produce xylonate, the engineered bacteria have received xylose and initially, by a dehydrogenase reaction by the xylose dehydrogenase enzyme, that converts it into an intermediate substance: xylonolactone. The xylonolactone is converted slowly and in a nonenzymatic reaction to xylonate. Xylonate is a five-carbon organic acid. Over the past few years, xylonate has been increasingly being considered as an important chemical due to its potential as an important chemical component. Xylonate has many applications that can be used in the food, chemical, and pharmaceutical industries. Specifically, xylonate can act as a precursor for the synthesis of D-1,2,4-Butanetriol and a decrease in concrete water. E.coli due to fast growth in cheap culture medium, having two enzymes for the bto synthesis and product production in lower 24 hours of fermentation was chosen as the target strain of genetic engineering and metabolism. This study aimed to clone and express xylose dehydrogenase from Caulobacter vibrioides in E.coli. Materials and Methods: At first, to access the bacterial gene sequence, the genome of the target bacterium was extracted. Then, to create a strain expressing the enzymes xylose dehydrogenase and xylonolactonase, the genes for these proteins were amplified from Caulobacter vibrioides CB1 and transferred to E. coli. For this purpose, the target genes were amplified using specifically designed primers via the Polymerase Chain Reaction (PCR) method and initially cloned into a pTZ57cloning vector and then subcloned into pET 26b expression vector. At the final step, the expression of the enzyme was assessed by SDS-PAGE, and the other confirmation was the reduction of NAD+ to NADH, which was used as an activity indicator of the enzyme, as investigated by a change in NADH absorbance at 340 nm. Results: Confirmatory tests were performed to ensure the presence of the gene in the vectors (using restriction enzymes and colony PCR for gene amplification). The expression and activity of the enzyme were analysed. The recombinant protein's presence was confirmed by SDS-PAGE for the xylose dehydrogenase gene, with a molecular weight of 52.2 kDa. The estimated recombinant protein expression levels were approximately 25%. Conclusion: The objective of this research was solely to establish the metabolic pathway for xylonate production in E. coli by surface expression of enzymes in this pathway (xylose dehydrogenase). The results obtained in this study confirm that half of the pathway is active at the cell surface, but further experiments are required to determine the precise production levels and complete the pathway. This study aimed to create a metabolic pathway for producing xylonate in E.coli.

Abstract Introduction: The construction of synthetic pathways within the framework of metabolic engineering is considered a modern approach in biotechnology, enabling the production of valuable compounds from natural biological resources. This strategy focuses on utilizing abundant biomaterials—particularly carbohydrates—for the industrial production of chemical compounds by modifying metabolic pathways in microorganisms. These processes can convert biomass derived from biological sources into fuels, chemicals, and polymers, thereby opening new opportunities for the sustainable production of chemical substances from renewable resources.
Aim: This study specifically focuses on the enzymatic production of benzoylformate decarboxylase (BFD) with the overarching goal of completing the enzymatic pathway for the biosynthesis of BT. This intricate pathway initiates with xylose as the primary carbon source and proceeds through a cascade of four distinct enzymatic reactions. Notably, Escherichia coli (E. coli), possessing two endogenous enzymes integral to this pathway, holds the potential for complete BT biosynthesis upon the introduction of the remaining two requisite genes. This research thus seeks to engineer E. coli as a robust biocatalyst for sustainable BT production. The strategic implementation of a fully functional enzymatic pathway within a well-characterized microbial host, such as  E. coli, promises a more environmentally benign and potentially more efficient route to BT synthesis compared to traditional chemical methods. Furthermore, the ability to manipulate and optimize the expression of these key enzymatic components within E. coli offers opportunities to enhance the overall yield and productivity of the bioproduction process. The successful establishment of such a system could pave the way for large-scale, cost-effective, and sustainable production of this valuable chemical intermediate.
Materials and Methods: To construct an E. coli strain capable of expressing the benzoylformate decarboxylase enzyme, the mdlC gene originating from Pseudomonas putida was amplified and subsequently cloned into both pBAD and pET28 expression vectors. Following the confirmation of successful cloning through rigorous confirmatory assays, protein expression was evaluated using Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE), and the enzymatic activity was assessed.
Results: Benzoylformate decarboxylase (BFD) is a pivotal enzyme within the engineered metabolic pathway for producing 1,2,4-butanetriol (BT) in   E.coli. In this study, the mdlC gene, encoding BFD from Pseudomonas putida, was successfully amplified and cloned into the versatile pBAD and the robust pET28 expression vectors. The pET28  system was preferred due to its ease of use and established track record in protein production, while the pBAD vector was strategically employed for its inducible expression capabilities, allowing for controlled protein synthesis. The expression of the  56 kDa target protein was confirmed through SDS-PAGE analysis, and the enzymatic function in the production of BT was subsequently verified using the sensitive and accurate HPLC method. This work lays a crucial foundation for the further optimization and development of a fully functional and efficient microbial cell factory for the sustainable production of this valuable chemical
Conclusion: The successful transfer of the expression construct into an appropriate E. coli host strain was confirmed by the presence of a distinct protein band at approximately 56 kDa on the SDS-PAGE gel, unequivocally verifying the expression of the mdlC gene. To evaluate the functional capacity of the expressed enzyme, the recombinant vector pBAD.mdlC was transformed into the E. coli TOP10 strain. The subsequent production of BT in the culture medium was meticulously analyzed using High-Performance Liquid Chromatography (HPLC).