Efficient bioproduction of 5-aminolevulinic acid, a promising biostimulant and nutrient, from renewable bioresources by engineered Corynebacterium glutamicum

Abstract

Background: 5-Aminolevulinic acid (5-ALA) is a promising biostimulant, feed nutrient, and photodynamic drug with wide applications in modern agriculture and therapy. Considering the complexity and low yield of chemical synthesis methods, bioproduction of 5-ALA has drawn intensive attention recently. However, the present bioproduction processes use refined glucose as the main carbon source and the production level still needs further enhancement. Results: To lay a solid technological foundation for large-scale commercialized bioproduction of 5-ALA, an industrial workhorse Corynebacterium glutamicum was metabolically engineered for high-level 5-ALA biosynthesis from cheap renewable bioresources. After evaluation of 5-ALA synthetases from different sources, the 5-ALA biosynthetic pathway and anaplerotic pathway were rebalanced by regulating intracellular activities of 5-ALA synthetase and phosphoenolpyruvate carboxylase. The engineered biocatalyst produced 5.5 g/L 5-ALA in shake flasks and 16.3 g/L in 5-L bioreactors with a one-step fermentation process from glucose. To lower the cost of feedstock, cheap raw materials were used to replace glucose. Enzymatically hydrolyzed cassava bagasse was proven to be a perfect alternative to refined sugars since the final 5-ALA titer further increased to 18.5 g/L. Use of corn starch hydrolysate resulted in a similar 5-ALA production level (16.0 g/L) with glucose, whereas use of beet molasses caused seriously inhibition. The results obtained here represent a new record of 5-ALA bioproduction. It is estimated that replacing glucose with cassava bagasse will reduce the carbon source cost by 90.1%. Conclusions: The high-level biosynthesis of 5-ALA from cheap bioresources will brighten the prospects for industrialization of this sustainable and environment-friendly process. The strategy for balancing metabolic flux developed in this study can also be used for improving the bioproduction of other value-added chemicals.

Managing Crop Load in European Pear (Pyrus communis L.)—A Review

“…The natural amino acid 5-aminolevulinic acid (ALA) has gained attention in agriculture, livestock production and medicine [75]. In a world where chemicals used in agriculture are coming under increasing scrutiny, it has been described as a natural, nontoxic, biodegradable, environmentally-friendly plant bioregulator [27] and is present in microbe, plant and animal cells [75,76] acting as an essential biosynthetic precursor of all organic heterocyclic tetrapyrrole molecules, including chlorophyll, heme and vitamin B12 [76].…”

“…As ALA is a non-toxic biodegradable amino acid present in living cells it is likely to meet modern environmental and food quality guidelines and thus has considerable potential as a chemical thinning agent, particularly if used at low concentrations. An efficient method of production of ALA has been described by Chen et al [75].…”

Metabolic engineering of microorganisms for the production of multifunctional non‐protein amino acids: γ‐aminobutyric acid and δ‐aminolevulinic acid

“…Up to now, the highest titre of GABA production by metabolic engineering is 308.26 g l ‐1 in E. coli through heterologously expressed gadB gene from L. lactis via GAD pathway (Yang et al ., 2018 ), while the highest titre of ALA bioproduction is 18.5 g l ‐1 in C. glutamicum through heterologously expressed ALAS ( hemA ) gene from R. palustris via C4 pathway (Chen et al ., 2020 ). However, these significant achievements realized by combining whole‐cell biocatalysts using 3 M glutamate as substrate and 4 g l ‐1 glycine supply respectively.…”

“…However, these significant achievements realized by combining whole‐cell biocatalysts using 3 M glutamate as substrate and 4 g l ‐1 glycine supply respectively. In fact, most of the GABA and ALA production contributed to the use of the complex medium in complicated cultivation process and continual feeding of the precursors (Feng et al ., 2016 ; Yang et al ., 2016 ; Li et al ., 2016a ; Hara et al ., 2019 ; Zhu et al ., 2019 ; Chen et al ., 2020 ). On the one hand, whole‐cell biocatalysts indeed remarkably enhance production, but depending on the amount of substrate and the number of cells uses.…”

Recent Progress on Chemical Production From Non-food Renewable Feedstocks Using Corynebacterium glutamicum

“…Additionally, enzymatic hydrolysis of cassava bagasse (contains (w/w) 50.3% starch, and 12.2% fiber, and 6.5% moisture) recovers approximately half the mass of glucose (0.53 g glucose/g cassava bagasse), which can then be utilized by engineered C. glutamicum. This produced 18.5 g/L of 5-aminolevulinic acid during fed-batch fermentation, exhibiting 90.1% thrift on the cost of carbon material (Chen et al, 2020). In addition to cassava, rice is another widely planted food crop that generates a hundred billion tons of waste straw in the harvested phase.…”