Improving flavour and quality of tomatoes by expression of synthetic gene encoding sweet protein monellin

Brazzein and Monellin: Chemical Analysis, Food Industry Applications, Safety and Quality Control, Nutritional Profile and Health Impacts

Recently, customers have been keener to buy products manufactured using all-natural ingredients with positive health properties, but without losing flavor. In this regard, the objective of the current study is to review the consumption of brazzein and monellin, their nutritional profiles and health effects, and their potential applications in the food industry. This poses challenges with sustainability and important quality and safety indicators, as well as the chemical processes used to determine them. To better understand the utilization of brazzein and monellin, the chemical analysis of these two natural sweet proteins was also reviewed by placing particular emphasis on their extraction methods, purification and structural characterization. Protein engineering is considered a means to improve the thermal stability of brazzein and monellin to enhance their application in food processing, especially where high temperatures are applied. When the quality and safety of these sweet proteins are well-investigated and the approval from safety authorities is secured, the market for brazzein and monellin as food ingredient substitutes for free sugar will be guaranteed in the future. Ultimately, the review on these two natural peptide sweeteners increases the body of knowledge on alleviating problems of obesity, diabetes and other non-communicable diseases.

Pseudomonas fluorescens imparts cadmium stress tolerance in Arabidopsis thaliana via induction of AtPCR2 gene expression

BACKGROUND

Cadmium is a non-essential, third largest heavy metal contaminant with long retention time that poses environmental hazards. It emanating majorly from industrial processes and phosphate fertilizers. Cadmium is effortlessly assimilated by plants and leads to yield loss. Henceforth, identification of mechanisms to attenuate the heavy metal toxicity in crops is beneficial for enhanced yields.

RESULTS

Beneficial soil bacteria have been known to combat both biotic and abiotic stress, thereby promoting plant growth. Amongst them, Pseudomonas fluorescens has been shown to enhance abiotic stress resistance in umpteen crops for instance maize and groundnut. Here, we investigated the role of P. fluorescens in conferring cadmium stress resistance in Arabidopsis thaliana. In silico analysis of PCR2 gene and promoter revealed the role, in cadmium stress resistance of A. thaliana. Real-time expression analysis employing qRT-PCR ratified the upregulation of AtPCR2 transcript under cadmium stress up to 6 folds. Total leaf (50%), biomass (23%), chlorophyll content (chlorophyll-a and b 40%, and 36 %) silique number (50%), and other growth parameters significantly improved on bacterial treatment of the 2mM Cd-stressed plants.

CONCLUSION

Moreover, generated 35s-promoter driven AtPCR2 over-expressing transgenic lines that exhibited resistance to cadmium and other heavy metal stress. Taken together, a crucial interplay of P. fluorscens mediated enhanced expression of AtPCR2 significantly induced cadmium stress resistance in Arabidopsis plants.

Transgenesis as a Tool for the Efficient Production of Selected Secondary Metabolites from in Vitro Plant Cultures

The plant kingdom abounds in countless species with potential medical uses. Many of them contain valuable secondary metabolites belonging to different classes and demonstrating anticancer, anti-inflammatory, antioxidant, antimicrobial or antidiabetic properties. Many of these metabolites, e.g., paclitaxel, vinblastine, betulinic acid, chlorogenic acid or ferrulic acid, have potential applications in medicine. Additionally, these compounds have many therapeutic and health-promoting properties. The growing demand for these plant secondary metabolites forces the use of new green biotechnology tools to create new, more productive in vitro transgenic plant cultures. These procedures have yielded many promising results, and transgenic cultures have been found to be safe, efficient and cost-effective sources of valuable secondary metabolites for medicine and industry. This review focuses on the use of various in vitro plant culture systems for the production of secondary metabolites.

High-level production of single chain monellin mutants with enhanced sweetness and stability in tobacco chloroplasts

MAIN CONCLUSION

Plastid-based MNEI protein mutants retain the structure, stability and sweetness of their bacterial counterparts, confirming the attractiveness of the plastid transformation technology for high-yield production of recombinant proteins. The prevalence of obesity and diabetes has dramatically increased the industrial demand for the development and use of alternatives to sugar and traditional sweeteners. Sweet proteins, such as MNEI, a single chain derivative of monellin, are the most promising candidates for industrial applications. In this work, we describe the use of tobacco chloroplasts as a stable plant expression platform to produce three MNEI protein mutants with improved taste profile and stability. All plant-based proteins were correctly expressed in tobacco chloroplasts, purified and subjected to in-depth chemical and sensory analyses. Recombinant MNEI mutants showed a protein yield ranging from 5% to more than 50% of total soluble proteins, which, to date, represents the highest accumulation level of MNEI mutants in plants. Comparative analyses demonstrated the high similarity, in terms of structure, stability and function, of the proteins produced in plant chloroplasts and bacteria. The high yield and the extreme sweetness perceived for the plant-derived proteins prove that plastid transformation technology is a safe, stable and cost-effective production platform for low-calorie sweeteners, with an estimated production of up to 25-30 mg of pure protein/plant.