Grains are a substantial source of macronutrients and energy for humans. Lactic acid (LA) fermentation is the oldest and most popular way to improve the functionality, nutritional value, taste, appearance and safety of cereal foods and reduce the energy required for cooking. This literature review discusses lactic acid fermentation of the most commonly used cereals and pseudocereals by examination of the microbiological and biochemical fundamentals of the process. The study provides a critical overview of the indispensable participation of lactic acid bacteria (LAB) in the production of many traditional, ethnic, ancient and modern fermented cereals and beverages, as the analysed literature covers 40 years. The results reveal that the functional aspects of LAB fermented foods are due to significant molecular changes in macronutrients during LA fermentation. Through the action of a vast microbial enzymatic pool, LAB form a broad spectrum of volatile compounds, bioactive peptides and oligosaccharides with prebiotic potential. Modern applications of this ancient bioprocess include the industrial production of probiotic sourdough, fortified pasta, cereal beverages and “boutique” pseudocereal bread. These goods are very promising in broadening the daily menu of consumers with special nutritional needs.

https://www.mdpi.com/2072-6643/12/4/1118/pdf

Lactic Acid Fermentation of Cereals and Pseudocereals: Ancient Nutritional Biotechnologies with Modern Applications

Acetoin and 2,3-butanediol (2,3-BD) have a large number of industrial applications. The production of acetoin and 2,3-BD has traditionally relied on oil supplies. Microbial production of acetoin and 2,3-BD will alleviate the dependence on oil. Acetoin and 2,3-BD are neighboring metabolites in the 2,3-BD metabolic pathway of bacteria. This review summarizes metabolic engineering strategies for improvement of microbial acetoin and 2,3-BD production. We also propose enhancements to current acetoin and 2,3-BD production strategies, by offering a metabolic engineering approach that is guided by systems biology and synthetic biology.

Metabolic engineering strategies for acetoin and 2,3-butanediol production: advances and prospects.

Review of direct chemical and biochemical transformations of starch.

2,3-Butanediol (2,3-BD) is an important starting material for the manufacture of bulk chemicals For efficient and large-scale production of 2,3-BD through fermentation, low-cost substrates are required One such substrate, inulin, is a polydisperse fructan found in a wide variety of plants In this study, a levanase with high inulinase activity and high pH and temperature stability was identified in Bacillus licheniformis strain ATCC 14580 B licheniformis strain ATCC 14580 was found to efficiently produce 2,3-BD from fructose at 50°C Then, the levanase was used for simultaneous saccharification and fermentation (SSF) of inulin to 2,3-BD A fed-batch SSF yielded 1030 g/liter 2,3-BD in 30 h, with a high productivity of 34 g/liter · h The results suggest that the SSF process developed with the thermophilic B licheniformis strain used might be a promising alternative for efficient 2,3-BD production from the favorable substrate inulin

Efficient Simultaneous Saccharification and Fermentation of Inulin to 2,3-Butanediol by Thermophilic Bacillus licheniformis ATCC 14580

Prospects on bio-based 2,3-butanediol and acetoin production: Recent progress and advances.

Toxic ingredients in food can lead to serious food-related diseases. Such compounds are bacterial toxins (Shiga-toxin, listeriolysin, Botulinum toxin), mycotoxins (aflatoxin, ochratoxin, zearalenone, fumonisin), pesticides of different classes (organochlorine, organophosphate, synthetic pyrethroids), heavy metals, and natural antinutrients such as phytates, oxalates, and cyanide-generating glycosides. The generally regarded safe (GRAS) status and long history of lactic acid bacteria (LAB) as essential ingredients of fermented foods and probiotics make them a major biological tool against a great variety of food-related toxins. This state-of-the-art review aims to summarize and discuss the data revealing the involvement of LAB in the detoxification of foods from hazardous agents of microbial and chemical nature. It is focused on the specific properties that allow LAB to counteract toxins and destroy them, as well as on the mechanisms of microbial antagonism toward toxigenic producers. Toxins of microbial origin are either adsorbed or degraded, toxic chemicals are hydrolyzed and then used as a carbon source, while heavy metals are bound and accumulated. Based on these comprehensive data, the prospects for developing new combinations of probiotic starters for food detoxification are considered.

/pdf/the-complex-role-of-lactic-acid-bacteria-in-food-2g2bbcy3.pdf

The Complex Role of Lactic Acid Bacteria in Food Detoxification

2,3-Butanediol (2,3-BD) is an organic compound, which is widely used as a fuel and fuel additive and applied in chemical, food, and pharmaceutical industries. Contemporary strategies for its economic synthesis include the development of microbial technologies that use starch as cheap and renewable feedstock. The present work encompasses the metabolic engineering of the excellent 2,3-BD producer Klebsiella pneumoniae G31. In order to perform direct starch conversion into 2,3-BD, the amyL gene encoding quite active, liquefying α-amylase in Bacillus licheniformis was cloned under lac promoter control in the recombinant K. pneumoniae G31-A. The enhanced extracellular over-expression of amyL led to the highest extracellular amylase activity (68 U/ml) ever detected in Klebsiella. The recombinant strain was capable of simultaneous saccharification and fermentation (SSF) of potato starch to 2,3-BD. In SSF batch process by the use of 200 g/l starch, the amount of total diols produced was 60.9 g/l (53.8 g/l 2,3-BD and 7.1 g/l acetoin), corresponding to 0.31 g/g conversion rate. The presented results are the first to show successful starch conversion to 2,3-BD by K. pneumoniae in a one-step process.

2,3-butanediol production from starch by engineered Klebsiella pneumoniae G31-A.

Highly butanol-tolerant strains have always been attractive because of their potential as microbial hosts for butanol production. However, due to the amphiphilic nature of 1-butanol as a solvent, the relationship between the cell surface hydrophobicity and butanol resistance remained ambiguous to date. In this work, the quantitatively estimated cell surface hydrophobicity of 74 Lactic acid bacteria strains were juxtaposed to their tolerance to various butanol concentrations. The obtained results revealed that the strains' hydrophobicity was inversely proportional to their butanol tolerance. All highly butanol-resistant strains were hydrophilic (cell surface hydrophobicity<1%), whereas the more hydrophobic the strains were, the more sensitive to butanol they were. Furthermore, cultivation at increasing butanol concentrations showed a clear tendency to decrease the level of hydrophobicity in all tested organisms, thus suggesting possible adaptation mechanisms. Purposeful reduction of cell surface hydrophobicity (by removal of S-layer proteins from the cell envelope) also led to an increase of butanol resistance. Since the results covered 23 different Lactic acid bacteria species of seven genera, it could be concluded that regardless of the species, the lower degree of cells' hydrophobicity clearly correlates with the higher level of butanol tolerance.

Low cell surface hydrophobicity is one of the key factors for high butanol tolerance of Lactic acid bacteria.

Bulgarian yogurt is usually associated with good health and longevity. This study aimed to analyse the current microbial content of homemade Bulgarian yogurt. Identification by 16S rDNA sequencing ...

https://www.tandfonline.com/doi/pdf/10.1080/13102818.2018.1475255

Microbial diversity and health-promoting properties of the traditional Bulgarian yogurt

Red microalgae represent a natural reservoir of beneficial substances with applications in different industrial sectors. They are rich in natural biomolecules known for their antihypertensive, antioxidant, antimicrobial, antiviral, anti-inflammatory, antitumor, and anticoagulant activities. Many red microalgae are a source of vitamins, minerals, photochemicals, polyunsaturated fatty acids, and a wide spectrum of polysaccharides. The content of their valuable compounds and their activities have turned red microalgae into cellular factories of special interest in food, nutraceutical, and pharmaceutical industries. Like all microalgae, the red ones are superior to traditional crops for the aims of biotechnology as they are renewable sources widely available in great quantities and are easy to culture. Moreover, some of the most studied red microalgae are generally recognized as safe. This review summarizes the valuable biochemicals from red microalgae and highlights their health and nutritional benefits.

/pdf/bioactive-compounds-from-red-microalgae-with-therapeutic-and-2vx04lsu.pdf

Flora Tsvetanova

Papers

The Complex Role of Lactic Acid Bacteria in Food Detoxification

2,3-butanediol production from starch by engineered Klebsiella pneumoniae G31-A.

Low cell surface hydrophobicity is one of the key factors for high butanol tolerance of Lactic acid bacteria.

Microbial diversity and health-promoting properties of the traditional Bulgarian yogurt

Bioactive Compounds from Red Microalgae with Therapeutic and Nutritional Value