Strategic intensification in butanol production by exogenous amino acid supplementation: Fermentation kinetics and thermodynamic studies

Exogenous ALA applied on different plant parts promotes tomato fruit quality and GABA synthesis

Introduction

Tomato fruit are rich in γ-aminobutyric acid (GABA), which lowers blood pressure and improves sleep. An increase in GABA content is important for enhancing the nutritional quality of tomato fruit.

Methods

To investigate the effects of 5-aminolevulinic acid (ALA) on fruit quality and GABA synthesis in greenhouse tomatoes, the tomato cultivar (Solanum lycopersicum cv. '184') was used as an experimental material. During the fruit-setting period, root drenching with 0, 10, and 50 mg·L-1 ALA, foliar spraying with 0, 50, and 100 mg·L-1 ALA, and fruit surface spraying with 0, 100, and 200 mg·L-1 ALA were applied. The study investigated the application of exogenous ALA to different parts of the plant to determine the optimal ALA concentrations for each application site (10 mg·L-1 for root application, 100 mg·L-1 for foliar application, and 100 mg·L-1 for fruit surface application). Using the selected optimal ALA concentrations, tomatoes were used to study the effects of exogenous ALA application at different sites on fruit quality and GABA synthesis of greenhouse tomatoes.

Results and discussion

The results demonstrated that exogenous ALA application to different parts of greenhouse-grown tomato plants substantially increased single-fruit weight by 42.37%-76.24%, soluble sugar content by 78.51%-94.52%, soluble solids by 9.09%-41.71%, soluble protein by 82.71%-241.05%, and ascorbic acid content by 1.31%-5.06% in mature tomatoes. And it reduced the organic acid content of the fruit by 12.81%-33.61%. Moreover, ALA applied at different parts of plants substantially enhanced the free amino acid content by 11.22%-16.50%, among them, umami amino acid content by 7.26%-20.13%. Besides, GABA content in mature tomato fruits was increased by 214.58%-433.32 across the different application parts. Exogenous ALA application at different sites regulates the activity of glutamate acid decarboxylase (GAD) and increases the content of glutamate for GABA synthesis pathway during tomato fruit development, thereby affecting the GABA content. In summary, exogenous ALA applied at different parts of tomato plants regulates the metabolism of amino acids and enhances the biosynthesis of GABA, which promotes the nutrient quality of the fruit.

Enhancing bacterial cellulose production of Komagataeibacter nataicola through fermented coconut water by Saccharomyces cerevisiae: A metabonomics approach

Nata de coco, an edible bacterial cellulose (BC) product, is a traditional dessert fermented in coconut water. Production of Nata de coco by Komagataeibacter nataicola is enhanced by pre-fermented coconut water, but its instability is a challenge. Here, BC production by K. nataicola Y19 was significantly improved by Saccharomyces cerevisiae 84-3 through shaping the metabolite profile of the coconut water. Different fermentation time with S. cerevisiae 84-3 resulted in distinct metabolite profiles and different promoting effect on BC yield. Compared to unfermented coconut water, coconut water fermented by S. cerevisiae 84-3 for 1d and 7d enhanced BC yield by 14.1-fold and 5.63-fold, respectively. Analysis between unfermented coconut water and 1d-fermented coconut water showed 129 significantly different metabolites, including organic acids, amino acids, nucleotides, and their derivatives. Prolonged fermentation for 7d changed levels of 155 metabolites belongs to organic acids, amino acids, nucleotides and their derivatives. Spearman correlation analysis further revealed that 17 metabolites were positively correlated with BC yield and 21 metabolites were negatively correlated with BC yield. These metabolites may affect energy metabolism, cell signaling, membrane integrity, and BC production by K. nataicola Y19. The further verification experiment gave the view that BC yield was not only closely related to the types of metabolites but also the concentration of metabolites. This study provides a novel theoretical framework for a highly efficient BC fermentation system utilizing stable fermented coconut water mediums.

ACETONE-BUTYL FERMENTATION PECULIARITIES OF THE BUTANOL STRAINS -PRODUCER

The aim of this review was to generalize and analyze the features of acetone-butyl fermentation as a type of butyric acid fermentation in the process of obtaining butanol as an alternative biofuel. Methods. The methods of analysis and generalization of analytical information and literature sources were used in the review. The results were obtained using the following methods such as microbiological (morphological properties of strains), chromatographic (determination of solvent concentration), spectrophotometric (determination of bacterial concentration), and molecular genetic (phylogenetic analysis of strains). Results. The process of acetone-butyl fermentation was analyzed, the main producer strains were considered, the features of the relationship between alcohol formation and sporulation were described, the possibility of butanol obtaining from synthesis gas was shown, and the features of the industrial production of butanol were considered. Conclusions. The features of the mechanism of acetone-butyl fermentation (the relationships between alcohol formation and sporulation, the duration of the acid-forming and alcohol-forming stages during batch fermentation depending on the change in the concentration of H2, CO, partial pressure, organic acids and mineral additives) and obtaining an enrichment culture during the production of butanol as an alternative fuel were shown. The possibility of using synthesis gas as a substrate for reducing atmospheric emissions during the fermentation process was shown. The direction of increasing the productivity of butanol-producing strains to create a competitive industrial biofuel technology was proposed.

Pathway dissection, regulation, engineering and application: lessons learned from biobutanol production by solventogenic clostridia

The global energy crisis and limited supply of petroleum fuels have rekindled the interest in utilizing a sustainable biomass to produce biofuel. Butanol, an advanced biofuel, is a superior renewable resource as it has a high energy content and is less hygroscopic than other candidates. At present, the biobutanol route, employing acetone-butanol-ethanol (ABE) fermentation in Clostridium species, is not economically competitive due to the high cost of feedstocks, low butanol titer, and product inhibition. Based on an analysis of the physiological characteristics of solventogenic clostridia, current advances that enhance ABE fermentation from strain improvement to product separation were systematically reviewed, focusing on: (1) elucidating the metabolic pathway and regulation mechanism of butanol synthesis; (2) enhancing cellular performance and robustness through metabolic engineering, and (3) optimizing the process of ABE fermentation. Finally, perspectives on engineering and exploiting clostridia as cell factories to efficiently produce various chemicals and materials are also discussed.