Improved trehalose production from biodiesel waste using parent and osmotically sensitive mutant of Propionibacterium freudenreichii subsp. shermanii under aerobic conditions

A comprehensive review on the properties, production, and applications of functional glucobioses

Glucobiose is a range of disaccharides consisting of two glucose molecules, generally including trehalose, kojibiose, sophorose, nigerose, laminaribiose, maltose, cellobiose, isomaltose, and gentiobiose. The difference glycosidic bonds of two glucose molecules result in the diverse molecular structures, physiochemical properties and physiological functions of these glucobioses. Some glucobioses are abundant in nature but have unconspicuous roles on health like maltose, whereas some rare glucobioses display remarkable biological effects. It is unpractical process to extract these rare glucobioses from natural resources, while biological synthesis is a feasible approach. Recently, the production and application of glucobiose have attracted considerable attention. This review provides a comprehensive overview of glucobioses, including their natural sources and physicochemical properties like structure, sweetness, digestive performance, toxicology, and cariogenicity. Specific enzymes used for the production of various glucobioses and fermentation production processes are summarized. Additionally, their versatile functions and broad applications are also introduced.

Glycerol as a substrate for actinobacteria of biotechnological interest: Advantages and perspectives in circular economy systems

Actinobacteria represent a ubiquitous group of microorganisms widely distributed in ecosystems. They have diverse physiological and metabolic properties, including the production of extracellular enzymes and a variety of secondary bioactive metabolites, such as antibiotics, immunosuppressants, and other compounds of industrial interest. Therefore, actinobacteria have been used for biotechnological purposes for more than three decades. The development of a biotechnological process requires the evaluation of its cost/benefit ratio, including the search for economic and efficient substrates for microorganisms development. Biodiesel is a clean, renewable, quality and economically viable source of energy, which also contributes to the conservation of the environment. Crude glycerol is the main by-product of biodiesel production and has many properties, so it has a commercial value that can be used to finance the biofuel production process. Actinobacteria can use glycerol as a source of carbon and energy, either pure o crude. A circular economy system aims to eliminate waste and pollution, keep products and materials in use, and regenerate natural systems. Although these principles are not yet met, some approaches are being made in this direction; the transformation of crude glycerol by actinobacteria is a process with great potential to be scaled on an industrial level. This review discusses the reports on glycerol as a promising source of carbon and energy for obtaining biomass and high-added value products by actinobacteria. Also, the factors influencing the biomass and secondary metabolites production in bioreactors are analyzed, and the tools available to overcome those that generate the main problems are discussed.

Use of Propionibacterium freudenreichii T82 Strain for Effective Biosynthesis of Propionic Acid and Trehalose in a Medium with Apple Pomace Extract and Potato Wastewater

Propionic acid bacteria are the source of many metabolites, e.g., propionic acid and trehalose. Compared to microbiological synthesis, the production of these metabolites by petrochemical means or enzymatic conversion is more profitable. The components of microbiological media account for a large part of the costs associated with propionic fermentation, due to the high nutritional requirements of Propionibacterium. This problem can be overcome by formulating a medium based on the by-products of technological processes, which can act as nutritional sources and at the same time replace expensive laboratory preparations (e.g., peptone and yeast extract). The metabolic activity of P. freudenreichii was investigated in two different breeding environments: in a medium containing peptone, yeast extract, and biotin, and in a waste-based medium consisting of only apple pomace and potato wastewater. The highest production of propionic acid amounting to 14.54 g/L was obtained in the medium containing apple pomace and pure laboratory supplements with a yield of 0.44 g/g. Importantly, the acid production parameters in the waste medium reached almost the same level (12.71 g/L, 0.42 g/g) as the medium containing pure supplements. Acetic acid synthesis was more efficient in the waste medium; it was also characterized by a higher level of accumulated trehalose (59.8 mg/g d.s.). Thus, the obtained results show that P. freudenreichii bacteria exhibited relatively high metabolic activity in an environment with apple pomace used as a carbon source and potato wastewater used as a nitrogen source. This method of propioniate production could be cheaper and more sustainable than the chemical manner.

Genome-scale model guided design of Propionibacterium for enhanced propionic acid production

Production of propionic acid by fermentation of propionibacteria has gained increasing attention in the past few years. However, biomanufacturing of propionic acid cannot compete with the current oxo-petrochemical synthesis process due to its well-established infrastructure, low oil prices and the high downstream purification costs of microbial production. Strain improvement to increase propionic acid yield is the best alternative to reduce downstream purification costs. The recent generation of genome-scale models for a number of Propionibacterium species facilitates the rational design of metabolic engineering strategies and provides a new opportunity to explore the metabolic potential of the Wood-Werkman cycle. Previous strategies for strain improvement have individually targeted acid tolerance, rate of propionate production or minimisation of by-products. Here we used the P. freudenreichii subsp. shermanii and the pan-Propionibacterium genome-scale metabolic models (GEMs) to simultaneously target these combined issues. This was achieved by focussing on strategies which yield higher energies and directly suppress acetate formation. Using P. freudenreichii subsp. shermanii, two strategies were assessed. The first tested the ability to manipulate the redox balance to favour propionate production by over-expressing the first two enzymes of the pentose-phosphate pathway (PPP), Zwf (glucose-6-phosphate 1-dehydrogenase) and Pgl (6-phosphogluconolactonase). Results showed a 4-fold increase in propionate to acetate ratio during the exponential growth phase. Secondly, the ability to enhance the energy yield from propionate production by over-expressing an ATP-dependent phosphoenolpyruvate carboxykinase (PEPCK) and sodium-pumping methylmalonyl-CoA decarboxylase (MMD) was tested, which extended the exponential growth phase. Together, these strategies demonstrate that in silico design strategies are predictive and can be used to reduce by-product formation in Propionibacterium. We also describe the benefit of carbon dioxide to propionibacteria growth, substrate conversion and propionate yield.

Propionibacterium spp.-source of propionic acid, vitamin B12, and other metabolites important for the industry

Bacteria from the Propionibacterium genus consists of two principal groups: cutaneous and classical. Cutaneous Propionibacterium are considered primary pathogens to humans, whereas classical Propionibacterium are widely used in the food and pharmaceutical industries. Bacteria from the Propionibacterium genus are capable of synthesizing numerous valuable compounds with a wide industrial usage. Biomass of the bacteria from the Propionibacterium genus constitutes sources of vitamins from the B group, including B12, trehalose, and numerous bacteriocins. These bacteria are also capable of synthesizing organic acids such as propionic acid and acetic acid. Because of GRAS status and their health-promoting characteristics, bacteria from the Propionibacterium genus and their metabolites (propionic acid, vitamin B12, and trehalose) are commonly used in the cosmetic, pharmaceutical, food, and other industries. They are also used as additives in fodders for livestock. In this review, we present the major species of Propionibacterium and their properties and provide an overview of their functions and applications. This review also presents current literature concerned with the possibilities of using Propionibacterium spp. to obtain valuable metabolites. It also presents the biosynthetic pathways as well as the impact of the genetic and environmental factors on the efficiency of their production.

Development of GRAS strains for nutraceutical production using systems and synthetic biology approaches: advances and prospects

Nutraceuticals are food substances with medical and health benefits for humans. Limited by complicated procedures, high cost, low yield, insufficient raw materials, resource waste, and environment pollution, chemical synthesis and extraction are being replaced by microbial synthesis of nutraceuticals. Many microbial strains that are generally regarded as safe (GRAS) have been identified and developed for the synthesis of nutraceuticals, and significant nutraceutical production by these strains has been achieved. In this review, we systematically summarize recent advances in nutraceutical research in terms of physiological effects on health, potential applications, drawbacks of traditional production processes, characteristics of production strains, and progress in microbial fermentation. Recent advances in systems and synthetic biology techniques have enabled comprehensive understanding of GRAS strains and its wider applications. Thus, these microbial strains are promising cell factories for the commercial production of nutraceuticals.

Bioconversion technologies of crude glycerol to value added industrial products

Crude glycerol that is produced as the by-product from biodiesel, has to be effectively utilized to contribute to the viability of biodiesel. Crude glycerol in large amounts can pose a threat to the environment. Therefore, there is a need to convert this crude glycerol into valued added products using biotechnological processes, which brings new revenue to biodiesel producers. Crude glycerol can serve as a feedstock for biopolymers, poly unsaturated fatty acids, ethanol, hydrogen and n-butanol production and as a raw material for different value added industrial products. Hence, in this review we have presented different bioconversion technologies of glycerol to value added industrial products.

Biocatalytic Production of Trehalose from Maltose by Using Whole Cells of Permeabilized Recombinant Escherichia coli

Trehalose is a non-reducing disaccharide, which can protect proteins, lipid membranes, and cells from desiccation, refrigeration, dehydration, and other harsh environments. Trehalose can be produced by different pathways and trehalose synthase pathway is a convenient, practical, and low-cost pathway for the industrial production of trehalose. In this study, 3 candidate treS genes were screened from genomic databases of Pseudomonas and expressed in Escherichia coli. One of them from P. stutzeri A1501 exhibited the best transformation ability from maltose into trehalose and the least byproduct. Thus, whole cells of this recombinant E. coli were used as biocatalyst for trehalose production. In order to improve the conversion rate of maltose to trehalose, optimization of the permeabilization and biotransformation were carried out. Under optimal conditions, 92.2 g/l trehalose was produced with a high productivity of 23.1 g/(l h). No increase of glucose was detected during the whole course. The biocatalytic process developed in this study might serve as a candidate for the large scale production of trehalose.

Engineering propionibacteria as versatile cell factories for the production of industrially important chemicals: advances, challenges, and prospects

Propionibacteria are actinobacteria consisting of two principal groups: cutaneous and dairy. Cutaneous propionibacteria are considered primary pathogens to humans, whereas dairy propionibacteria are widely used in the food and pharmaceutical industries. Increasing attention has been focused on improving the performance of dairy propionibacteria for the production of industrially important chemicals, and significant advances have been made through strain engineering and process optimization in the production of flavor compounds, nutraceuticals, and antimicrobial compounds. In addition, genome sequencing of several propionibacteria species has been completed, deepening understanding of the metabolic and physiological features of these organisms. However, the metabolic engineering of propionibacteria still faces several challenges owing to the lack of efficient genome manipulation tools and the existence of various types of strong restriction-modification systems. The emergence of systems and synthetic biology provides new opportunities to overcome these bottlenecks. In this review, we first introduce the major species of propionibacteria and their properties and provide an overview of their functions and applications. We then discuss advances in the genome sequencing and metabolic engineering of these bacteria. Finally, we discuss systems and synthetic biology approaches for engineering propionibacteria as efficient and robust cell factories for the production of industrially important chemicals.

Trends in bacterial trehalose metabolism and significant nodes of metabolic pathway in the direction of trehalose accumulation

Summary

The current knowledge of trehalose biosynthesis under stress conditions is incomplete and needs further research. Since trehalose finds industrial and pharmaceutical applications, enhanced accumulation of trehalose in bacteria seems advantageous for commercial production. Moreover, physiological role of trehalose is a key to generate stress resistant bacteria by metabolic engineering. Although trehalose biosynthesis requires few metabolites and enzyme reactions, it appears to have a more complex metabolic regulation. Trehalose biosynthesis in bacteria is known through three pathways – OtsAB, TreYZ and TreS. The interconnections of in vivo synthesis of trehalose, glycogen or maltose were most interesting to investigate in recent years. Further, enzymes at different nodes (glucose-6-P, glucose-1-P and NDP-glucose) of metabolic pathways influence enhancement of trehalose accumulation. Most of the study of trehalose biosynthesis was explored in medically significant Mycobacterium, research model Escherichia coli, industrially applicable Corynebacterium and food and probiotic interest Propionibacterium freudenreichii. Therefore, the present review dealt with the trehalose metabolism in these bacteria. In addition, an effort was made to recognize how enzymes at different nodes of metabolic pathway can influence trehalose accumulation.

Multifaceted attributes of dairy propionibacteria: a review

Dairy propionibacteria are Generally Recognized as Safe (GRAS) status microorganisms which have been traditionally used for the manufacture of Swiss type cheeses. In the last two decades various added features and functionalities have been discovered and developed from these bacteria. Propionibacteria are robust organisms with remarkable adaptability to technological and physiological stress conditions. Besides, they also display a multitude of health promoting properties like modulation of gut microbiota, improved gut physiology and immunomodulation suggesting their promising probiotic potential. Propionibacteria produce an interestingly wide range of functional biomolecules like B group vitamins, trehalose, conjugated linoleic acid, propionic acid, bacteriocins, bifidogenic factors etc. These bacteria are thus now being explored for designing novel functional foods as well as for industrial production of nutraceuticals. Growing interest in these bacteria is fueled by the first whole genome sequencing of a Propionibacterium freudenreichii strain providing a platform for better understanding of various pathways and further improvement in related process technologies.