A preliminary study on l-lysine fermentation from lignocellulose feedstock and techno-economic evaluation

Innovative approaches for amino acid production via consolidated bioprocessing of agricultural biomass

Agricultural plantations in Indonesia and Malaysia yield substantial waste, necessitating proper disposal to address environmental concerns. Yet, these wastes, rich in starch and lignocellulosic content, offer an opportunity for value-added product development, particularly amino acid production. Traditional methods often rely on costly commercial enzymes to convert biomass into fermentable sugars for amino acid production. An alternative, consolidated bioprocessing, enables the direct conversion of agricultural biomass into amino acids using selected microorganisms. This review provides a comprehensive assessment of the potential of agricultural biomass in Indonesia and Malaysia for amino acid production through consolidated bioprocessing. It explores suitable microorganisms and presents a case study on using Bacillus subtilis ATCC 6051 to produce 9.56 mg/mL of amino acids directly from pineapple plant stems. These findings contribute to the advancement of sustainable amino acid production methods using agricultural biomass especially in Indonesia and Malaysia through consolidated bioprocessing, reducing waste and enhancing environmental sustainability.

A comprehensive review on the biological conversion of lignocellulosic biomass into hydrogen: Pretreatment strategy, technology advances and perspectives

The globe has dependent on energy generation and utilization for many years; conversely, ecological concerns constrained the world to view hydrogen as an alternative for economic development. Lignocellulosic biomass is broadly accessible as a low-cost renewable feedstock and nonreactive nature; it has received a lot of consideration as a global energy source and the most attractive alternative to replace fossil natural substances for energy production. Pretreatment of lignocellulosic biomass is essential to advance its fragmentation and lower the lignin content for sustainable energy generation. This review's goal is to provide the different pretreatment strategies for enlarging the solubility and surface area of lignocellulosic biomass. The biological conversion of lignocellulosic biomass to hydrogen was reviewed and operational conditions and enhancing methods were discussed. This review summarizes the working conditions, parameters, yield percentages, techno-economic analysis, challenges, and future recommendations on the direct conversion of biomass to hydrogen.

Strategy for the design of a bioreactor for L-lysine immobilized fermentation using Corynebacterium glutamicum

Biofilm-immobilized fermentation is a novel strategy that has been utilized in L-lysine fermentation. In this study, we describe a strategy for designing bioreactors for immobilized fermentation. We have constructed steel structures in which the carriers can be sewn, forming several star-like structures with different angles, and changing the ventilation robot to the aeration tray. In a 10-L bioreactor, this structure with 12 angles assisted the immobilized system to remedy the gap between free-cell and immobilized fermentation in the conversion rate. In a 50-L bioreactor, this enlarged structure with 16 angles illustrated a 4.61% higher conversion rate than the free-cell fermentation (67.75%) and increased the production by 28.56%. This successful case is the first step towards to industrial production of biofilm-based immobilized fermentation.Key points• The designed steel structure is useful for L-lysine immobilized fermentation in a 10-L bioreactor.• The conversion rate of immobilized fermentation increased from 13.99 to 60.07% and is 1.03% higher than that of the free-cell fermentation.• The conversion rate of the redesigned 50-L bioreactor is higher than that of free-cell fermentation.

Metabolic Engineering for Valorization of Agri- and Aqua-Culture Sidestreams for Production of Nitrogenous Compounds by Corynebacterium glutamicum

Corynebacterium glutamicum is used for the million-ton-scale production of amino acids. Valorization of sidestreams from agri- and aqua-culture has focused on the production of biofuels and carboxylic acids. Nitrogen present in various amounts in sidestreams may be valuable for the production of amines, amino acids and other nitrogenous compounds. Metabolic engineering of C. glutamicum for valorization of agri- and aqua-culture sidestreams addresses to bridge this gap. The product portfolio accessible via C. glutamicum fermentation primarily features amino acids and diamines for large-volume markets in addition to various specialty amines. On the one hand, this review covers metabolic engineering of C. glutamicum to efficiently utilize components of various sidestreams. On the other hand, examples of the design and implementation of synthetic pathways not present in native metabolism to produce sought after nitrogenous compounds will be provided. Perspectives and challenges of this concept will be discussed.

Cascaded valorization of brown seaweed to produce l-lysine and value-added products using Corynebacterium glutamicum streamlined by systems metabolic engineering

Seaweeds emerge as promising third-generation renewable for sustainable bioproduction. In the present work, we valorized brown seaweed to produce l-lysine, the world's leading feed amino acid, using Corynebacterium glutamicum, which was streamlined by systems metabolic engineering. The mutant C. glutamicum SEA-1 served as a starting point for development because it produced small amounts of l-lysine from mannitol, a major seaweed sugar, because of the deletion of its arabitol repressor AtlR and its engineered l-lysine pathway. Starting from SEA-1, we systematically optimized the microbe to redirect excess NADH, formed on the sugar alcohol, towards NADPH, required for l-lysine synthesis. The mannitol dehydrogenase variant MtlD D75A, inspired by 3D protein homology modelling, partly generated NADPH during the oxidation of mannitol to fructose, leading to a 70% increased l-lysine yield in strain SEA-2C. Several rounds of strain engineering further increased NADPH supply and l-lysine production. The best strain, SEA-7, overexpressed the membrane-bound transhydrogenase pntAB together with codon-optimized gapN, encoding NADPH-dependent glyceraldehyde 3-phosphate dehydrogenase, and mak, encoding fructokinase. In a fed-batch process, SEA-7 produced 76 g L^-1l-lysine from mannitol at a yield of 0.26 mol mol^-1 and a maximum productivity of 2.1 g L^-1 h^-1. Finally, SEA-7 was integrated into seaweed valorization cascades. Aqua-cultured Laminaria digitata, a major seaweed for commercial alginate, was extracted and hydrolyzed enzymatically, followed by recovery and clean-up of pure alginate gum. The residual sugar-based mixture was converted to l-lysine at a yield of 0.27 C-mol C-mol^-1 using SEA-7. Second, stems of the wild-harvested seaweed Durvillaea antarctica, obtained as waste during commercial processing of the blades for human consumption, were extracted using acid treatment. Fermentation of the hydrolysate using SEA-7 provided l-lysine at a yield of 0.40 C-mol C-mol^-1. Our findings enable improvement of the efficiency of seaweed biorefineries using tailor-made C. glutamicum strains.

Highly efficient biosynthesis of l-ornithine from mannitol by using recombinant Corynebacterium glutamicum

Mannitol is a promising six-carbon sugar alcohol that is widely found in macroalgae. The potential of mannitol as a renewable raw material is of interest due to the advantages of ocean farms. Herein, the biobased production of l-ornithine from mannitol was resoundingly demonstrated for the first time in engineered Corynebacterium glutamicum S9114 through the deletion of the mannitol repressor MtlR. By modulating the expression of mtlD and reinforcing the fructose metabolic pathway, we generated the strain MTL13 that produced 54.56 g/L of l-ornithine with a yield of 0.47 g/g on mannitol. These results illustrate the robust conversion from mannitol to l-ornithine using engineered Corynebacterium glutamicum, providing a reference for the biobased production of additional chemicals from mannitol.

Lysine Production by Dry Biorefining of Wheat Straw and Cofermentation of Corynebacterium glutamicum

A preliminary study shows that lysine production from lignocellulose feedstock is feasible, but the conversion of xylose in lignocellulose to lysine remains unsolved. Two technical barriers are responsible for the remaining xylose conversion: one is the xylose loss into the wastewater stream of the biorefinery processing chain, and the other is the lack of efficient lysine-producing strain with xylose utilization. Here, we conducted a new biorefinery approach of consequent dry acid pretreatment and biodetoxification, resulting in zero wastewater generation and then well-preserved xylose. To provide the lysine-producing strain with xylose utilization, we modified the Corynebacterium glutamicum by establishing the xylose assimilation pathway and improving the NADPH cofactor regeneration. The combinational modification of biorefinery processing and strain development led to 31.3 g/L of lysine production with a yield of 0.23 g lysine per gram of wheat straw derived sugars. This study provides a practical method for upgraded lysine production from lignocellulose for future industrial applications.

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

Due to the non-renewable nature of fossil fuels, microbial fermentation is considered a sustainable approach for chemical production using glucose, xylose, menthol, and other complex carbon sources represented by lignocellulosic biomass. Among these, xylose, methanol, arabinose, glycerol, and other alternative feedstocks have been identified as superior non-food sustainable carbon substrates that can be effectively developed for microbe-based bioproduction. Corynebacterium glutamicum is a model gram-positive bacterium that has been extensively engineered to produce amino acids and other chemicals. Recently, in order to reduce production costs and avoid competition for human food, C. glutamicum has also been engineered to broaden its substrate spectrum. Strengthening endogenous metabolic pathways or assembling heterologous ones enables C. glutamicum to rapidly catabolize a multitude of carbon sources. This review summarizes recent progress in metabolic engineering of C. glutamicum toward a broad substrate spectrum and diverse chemical production. In particularly, utilization of lignocellulosic biomass-derived complex hybrid carbon source represents the futural direction for non-food renewable feedstocks was discussed.

Tailoring Activated Carbons for Efficient Downstream Processing: Selective Liquid-Phase Adsorption of Lysine

The essential amino acid lysine is of great importance in the nutrition and pharmaceutical industries and is mainly produced in biorefineries by the fermentation of glucose. In biorefineries, downstream processing is often the most energy-consuming step. Adsorption on hydrophobic adsorbents represents an energy, resource, and cost-saving alternative. The results reported herein provide insights into the selective separation of l-lysine from aqueous solution by liquid-phase adsorption using tailored activated carbons. A variety of commercial activated carbons with different textural properties and surface functionalities is investigated. Comprehensive adsorbent characterization establishes structure-adsorption relationships that define the major roles of the specific surface area and oxygen functionalities. A 13-fold increase of the separation of lysine and glucose is achieved through systematic modification of a selected activated carbon by oxidation, and lysine adsorption is enhanced by 30 %.

High-efficiency and low-cost production of cadaverine from a permeabilized-cell bioconversion by a Lysine-induced engineered Escherichia coli

Cadaverine is the monomer of bio-based nylons polyamide 5.4, 5.6 and 5.10. In this study, a litre-scale integrated strategy was developed for high-efficiency and low-cost production of cadaverine using an engineered Escherichia coli. Firstly, the engineered strain BL21-P_cad-CadA induced by cheap l-lysine-HCl instead of IPTG was constructed. Then the permeabilized cells were served as the biocatalyst for the production of cadaverine, because the enhanced permeability facilitated the mass transfer of the substrate and the release of products. After the replacement of industrial materials and the solution of the scale-up permeabilization process, cadaverine concentration reached 205 g/L with the yield of 92.1% after 20 h in a 2 L bioconversion system, achieving the level of industrial production. Furthermore, the costs of industrial materials for 2 L integrated strategy ($2.78) was only 1/11 of the lab reagents ($30.88). Therefore, the proposed strategy is a promising candidate for the industrial process of cadaverine.

Microbial extraction of biotin from lignocellulose biomass and its application on glutamic acid production

Biotin (vitamin B₇) is an important nutrient for various fermentations. It is abundant in agricultural lignocellulose biomass and maintains stable in biorefinery processing chain including acid pretreatment, biodetoxification and saccharification. Here we show a microbial extraction of biotin from biotin-rich corn leaves hydrolysate. Corynebacterium glutamicum was found to have the highest biotin uptake capacity among different biotin auxotrophic microorganisms, and it was further significantly increased by overexpressing the bioYMN gene cluster encoding biotin transporter. Finally 250 folds greater biotin was extracted by recombinant C. glutamicum (303.8 mg/kg dry cell) from virgin corn leaves (1.2 mg/kg), which was far higher than that in commonly used fermentation additives including yeast extract (∼2 mg/kg), molasses (∼1 mg/kg) and corn steep liquor (∼0.75 mg/kg). The biotin extracted from corn leaves was successfully applied to glutamic acid fermentation. This is the first report on microbial extraction of biotin from lignocellulose biomass and fermentation promotion application.

Metabolic engineering of Corynebacterium glutamicum S9114 to enhance the production of l-ornithine driven by glucose and xylose

l-ornithine, an important amino acid, is widely used in food and medicine industries. l-ornithine production mainly relies on microbial fermentation, which may not meet the industrial requirement owing to the poor fermentation ability of available strains. Herein, mscCG2 deletion, CgS9114_12202 (gdh2) overexpression and rational modulation in tricarboxylic acid cycle was firstly demonstrated to increase l-ornithine production in engineered Corynebacterium glutamicum S9114. By further modulate glucose utility result in strain SO26 that produced 38.5 g/L or 43.6 g/L of l-ornithine in shake flask and fed-batch fermentation, respectively. This was 25% higher than that of the original strain (30.8 g/L) and exhibits highest titer reported in shake-flask. Moreover, the incorporation of xylose pathway in the engineered strain resulted in the highest l-ornithine production titer (18.9 g/L) and yield (0.40 g/g xylose) with xylose substrate. These results illustrate the tremendous potential of the engineered strain C. glutamicum S9114 in l-ornithine production.

Process optimization and kinetic analysis of malic acid production from crude glycerol using Aspergillus niger

In the present work, optimization of crude glycerol fermentation to produce malic acid by using Aspergillus niger was investigated using response surface methodology and artificial neural network. Kinetic investigation of bioconversion of crude glycerol into malic acid using Aspergillus niger was studied using Monod, Mosser, and Haldane-Andrew models. Crude glycerol concentration, initial pH and yeast extract concentration were found to be significant compounds affecting malic acid production by Aspergillus niger. Both dry cell weight and malic acid titre were found decreased with increase in crude glycerol concentration. Haldane-Andrew model gave the best fit for the production of malic acid from crude glycerol with µ_max of 0.1542 h^-1. The maximum malic acid production obtained under optimum conditions was 92.64 + 1.54 g/L after 192 h from crude glycerol using Aspergillus niger.

Metabolic engineering advances and prospects for amino acid production

Amino acid fermentation is one of the major pillars of industrial biotechnology. The multi-billion USD amino acid market is rising steadily and is diversifying. Metabolic engineering is no longer focused solely on strain development for the bulk amino acids L-glutamate and L-lysine that are produced at the million-ton scale, but targets specialty amino acids. These demands are met by the development and application of new metabolic engineering tools including CRISPR and biosensor technologies as well as production processes by enabling a flexible feedstock concept, co-production and co-cultivation schemes. Metabolic engineering advances are exemplified for specialty proteinogenic amino acids, cyclic amino acids, omega-amino acids, and amino acids functionalized by hydroxylation, halogenation and N-methylation.