The richness and diversity of protein rich fermented foods are chiefly observed in many Asian countries. They are potential source of wide range of biologically active peptides depending on the protein source and starter culture used for fermentation. The major protein rich fermented foods popularly consumed in Asian countries include fermented soybean, fermented milk and fermented fish products. These foods are fermented using different starter cultures including lactic acid bacteria (LAB), Bacillus species, yeast and filamentous fungi. Fermentation by individual starter culture results in unique products by a series of enzymatic hydrolysis, leading to production of a diversity of bioactive peptides responsible for health benefits. Bioactive peptides in Asian protein rich fermented foods have been reported for exhibiting antihypertensive, antioxidant, antibacterial, antidiabetic and anticancer properties. This review is focused on Asian protein rich fermented foods, associated microbes and bioactive peptides responsible for health benefits.
Lactic acid bacteria (LAB) are non-mobile, gram-positive, non-spore-forming, micro-aerophilic microorganisms widely explored as starter cultures food industry to enhance the gustatory, nutritional value, imparts appetizing flavour, texture to milk, vegetative, meat foods and prolongs their shelf life. This vast review emphasis various LABs widely explored in the food industry. Herein, we have summarized the classification of LAB strains, their metabolic pathways for biosynthesis of lactic acid, ethanol, acetic acid and demonstrated their application in various food industries for making fermented milk (yoghurt), cheese, beverages, bread, and animal foods. The wide spectrum of LAB-based probiotics, bacteriocins, exopolysaccharides, bio preservative and their relevant benefits towards human health has also been discussed. Moreover, LAB bacteriocins and probiotics in food application may limit the growth of pathogenic, while boosting health immunity. Microbial exopolysaccharides have interesting characteristics for the fermented food industry as new functional foods. Later on, we have discussed the various advancement in metabolic engineering, synthetic biology tools, which have gained considerable interest to elucidate the biosynthetic pathway for tailoring cellular metabolism for high activity.
In recent years, the biological functions of human milk oligosaccharides and the potential toxic effects of red meat on human health have attracted considerable attention. Sialic acid is an important carbohydrate in milk and red meat, corresponding to sialylated oligosaccharides and N-glycolylneuraminic acid (NeuGc, one type of sialic acid). Herein, we reviewed the metabolic fate of dietary sialic acid in the body and their effects on gut and oral microbes. In summary, dietary NeuAc monomer is directly excreted through urine after being assimilated through the intestines and is not utilized by the human body; in contrast, dietary NeuGc from red meat is easily utilized by the human body and can be incorporated into the brain and other organs. Sialoglycans can be partially utilized by the human body, but they do not affect the cognitive development and growth of children. Dietary sialic acid may mainly regulate the growth and metabolism of gastrointestinal microbiota and human health and development through the gut–brain axis.
Biorefineries contribute to a circular bioeconomy using renewable feedstock to produce commodity and specialty chemicals as an alternative to petroleum chemicals. Using waste streams such as food waste and agricultural waste as a feedstock for biorefineries is a promising approach for obtaining value-added products in an economically feasible and sustainable way. The conversion of biomass to chemicals offers diverse opportunities but poses new technological challenges. This paper aims to review the current state of food and agricultural waste valorisation by giving a brief technical overview, summarizing the current state of the bio-based market, and identifying the current barriers to scaling-up biorefineries. Utilizing lignocellulosic biomass in biorefineries calls for pre-treatment due to its complex structure, in which biomass is broken into monosaccharides, building blocks of value-added products. Different state of the art technologies for lignocellulose pre-treatment is introduced in the review followed by a brief explanation of the role of the hydrolysis and fermentation. The economic aspect of chemical production from biomass waste at an industrial scale is also introduced by giving an overview of some recent techno-economic studies.
Wastewaters from various process industries, namely food and agricultural, sugar mill, brewery, milk, vegetable and fruit, and meat and fisheries processing industries and their wastewater effluents contain nutrients, organic matter, inorganic, heavy metals, suspended solids, and pathogens. The discharges of non-treated wastewater enter the nearby aquatic ecosystem (e.g., lakes, rivers) and are a significant concern due to the presence of different nutrients, competing ions and C containing pollutants. It causes excessive growth of algae, loss of habitat/species, and other negative impacts on human health/environment. In the present review, different treatment approaches have been discussed in utilizing these nutrients to synthesize value-added products such as biopolymer, biofuel, pigment, organic acid, or enzymes. These biopolymers can be used to prepare various food products/packaging materials. Dextran, chitosan, carrageenan, alginate, and pectin are good examples of non-food biopolymers. Besides these products, poly-β-hydroxybutyrate (PHB) synthesis from wastewater nutrients is reported as a new source of bio-nanocomposite materials/biopolymer-based coatings. In this review, the different treatment approaches are discussed, which are being used worldwide for the removal/recovery of nutrients, toxic pollutants, and the potential resource recovery of value-added products from wastewater.
Industrial-scale bioprocessing underpins much of the production of pharmaceuticals, nutraceuticals, food, and beverage processing industries of the modern world. The profitability of these processes increasingly leverages the economies of scale and scope that are critically dependent on the product yields, titers, and productivity. Most of the processes are controlled using classical control approaches and represent over 90% of the industrial controls used in bioprocessing industries. However, with the advances in the production processes, especially in the biopharmaceutical and nutraceutical industries, monitoring and control of bioprocesses such as fermentations with GMO organisms, and downstream processing has become increasingly complex and the inadequacies of the classical and some of the modern control systems techniques is becoming apparent. Therefore, with increasing research complexity, nonlinearity, and digitization in process, there has been a critical need for advanced process control that is more effective, and easier process intensification and product yield (both by quality and quantity) can be achieved. In this review, industrial aspects of a process and automation along with various commercial control strategies have been extensively discussed to give an insight into the future prospects of industrial development and possible new strategies for process control and automation with a special focus on the biopharmaceutical industry.
Cellulose is the utmost plenteous source of biopolymer in our earth, and fungi are the most efficient and ubiquitous organism in degrading the cellulosic biomass by synthesizing cellulases. Tailoring through genetic manipulation has played a substantial role in constructing novel fungal strains towards improved cellulase production of desired traits. However, the traditional methods of genetic manipulation of fungi are time-consuming and tedious. With the availability of the full-genome sequences of several industrially relevant filamentous fungi, CRISPR-CAS (clustered regularly interspaced short palindromic repeats/CRISPR-associated protein) technology has come into the focus for the proficient development of manipulated strains of filamentous fungi. This review summarizes the mode of action of cellulases, transcription level regulation for cellulase expression, various traditional strategies of genetic manipulation with CRISPR-CAS technology to develop modified fungal strains for a preferred level of cellulase production, and the futuristic trend in this arena of research.
N-Acetyl-d-neuraminic acid (NeuAc), a well-known and well-studied sialic acid, is found in cell surface glycolipids and glycoproteins, where it performs a variety of biological functions. The use of NeuAc as a nutraceutical for infant brain development and as an intermediate for pharmaceutical production demands its production on an industrial scale. Natural extraction, chemical synthesis, enzymatic synthesis, and biosynthesis are the methods used for NeuAc production. Among these methods, enzymatic synthesis using N-acetyl-glucosamine (GlcNAc) 2-epimerase (AGE) for epimerization and N-acetyl-d-neuraminic acid lyase (NAL) for aldol condensation, has been reported to produce NeuAc with high production efficiency. In this review, we discuss advances in the two-step enzymatic synthesis of NeuAc using pyruvate and GlcNAc as substrates. The major challenges in producing NeuAc with high yield are highlighted, including multiple parameter-dependent processes, undesirable reversibility, and diminished solubility of AGEs and NALs. Further, different strategies applied to overcome the limitations of the two-step enzymatic production are discussed, such as pyruvate concentration and temperature shift during the process to increase conversion yield, use of mathematical and computational simulations for process optimization, enzyme engineering to make enzymes highly efficient, and the use of tags and chaperones to increase enzyme solubility. We suggest future directions and the strategies that can be followed to improve enzymatic synthesis of NeuAc.
The popularity of traditional fermented food products is based on their healthiness. The addition of a starter brings consistent, desirable, and predictable food changes with improved nutritive, functional, and sensory qualities. The addition of a mixture of plant residues as a starter or source of microbes is an age-old practice to prepare traditional fermented food and beverages, and most of the reported data on traditional foods were based on the analysis of the final product. The contribution of an individual starter component (plant residue) is not experimentally substantiated for any traditional fermented food, but this data are very essential for the formulation of an effective starter. In this study, Asparagus racemosus, which used as a common ingredient of starter for preparation of rice fermented food in the Indian sub-continent, was used as a starter for the preparation of rice fermented food under laboratory scale, and its microbial and nutrient profile was evaluated. The fermented product was a good source of lactic acid bacteria, Bifidobacterium sp., yeast, etc. The food product was acidic and enriched with lactic acid and acetic acid with titratable acidity of 0.65%. The content of protein, fat, minerals, and vitamins (water-soluble) was considerably improved. Most notably, oligosaccharide (G3-matotriose), unsaturated fatty acids (ω3, ω6, ω7, and ω9), and a pool of essential and non-essential amino acids were enriched in the newly formulated food. Thus, the herbal starter-based rice fermented food would provide important macro- and micronutrients. They could also deliver large numbers of active microorganisms for the sustainability of health. Therefore, the selected plant part conferred its suitability as an effective starter for the preparation of healthier rice-based food products.
L-Aspartate β-decarboxylase from Acinetobacter radioresistens (ArASD) has been modified to convert 3-methylaspartic acid into 2-aminobutyric acid, which activated a novel process for biosynthesis of 2-aminobutyric acid. However, the process is limited by the low activity of the ArASD. Here, the activity of ArASD was significantly improved by modification based on sequence alignment and structural analysis. The 38th residue of ArASD is speculated to be the key residue for regulating the conformation of the internal aldimine, and site-directed mutagenesis on R38 residue was carried out. A variant, K18A/R38K/V287I, with 2.2 times higher specific activity was isolated. Molecular dynamics simulation indicated that the torsion angle of the imine bond of the variant decreased, which was beneficial to the protonation of the internal aldimine and the increase in the initial energy of the enzyme. Therefore, the energy barrier of the transition state was reduced, resulting in improved catalytic activity toward 3-methylaspartic acid. These results provide a reference and a new point of view for enzyme modification by increasing the energy of the initial state.
Escherichia coli is a model organism with a clear genetic background that is widely used in metabolic engineering and synthetic biology research. To gain a complete picture of the complexly metabolic and regulatory interactions in E. coli, researchers often need to retrieve information from various databases which cover different types of interactions. A central one-stop service integrating various molecular interactions in E. coli would be helpful for the community. We constructed a database called E. coli integrated network (EcoIN) by integrating known molecular interaction information from databases and literature. EcoIN contains nearly 160,000 pairs of interactions and users can easily search the different types of interacting partners for a metabolite, gene or protein, and thus gain access to a more comprehensive interaction map of E. coli. To illustrate the application of EcoIN, we used the full path algorithm to identify metabolic feedback/feedforward regulatory loops having at least two different types of regulatory interactions. Applying this algorithm to analyze the regulatory loops for the amino acid biosynthetic pathways, we found some multi-step regulation loops which may affect the metabolic flux and are potential new engineering targets. The EcoIN database is freely accessible at http://ecoin.ibiodesign.net/ and analysis codes are available at GitHub: https://github.com/maozhitao/EcoIN.
The glutamate decarboxylase (Gad) system is an important amino acid-dependent acid resistance system commonly found in microorganisms. Actinobacillus succinogenes is one of the best natural producers of succinic acid (SA) but lacks glutamate decarboxylase. This study assessed the effects of Gad system introduction into A. succinogenes. The recombinant strains gadB-SW and gadBC-SW were constructed by heterologous expression of gadB alone, or gadB together with gadC, respectively. After 1.0 and 1.5 h of acid stress at pH 4.6, cell survival of gadBC-SW was greater than gadB-SW. The growth of gadB-SW and gadBC-SW was both affected by the expression of heterologous proteins and by γ-aminobutyric acid, with gadBC-SW growth reduced at a neutral pH. SA production in acidic conditions was evaluated by a shake flask and by 3-L bioreactor fermentation. The results showed gadBC-SW to increase SA production by 8.4% in shake flask compared to the parent strain, SW. For a 3-L bioreactor batch fermentation under acidic environment, the highest conversion rate of sugar to SA was observed for gadBC-SW, reaching 96%. However, SA concentration by gadBC-SW was only 47 g/L and 31 g/L at pH 6.5 and pH 6.0, respectively. In summary, the introduction of heterologous gadB and gadC into A. succinogenes not only improved acid tolerance but also influenced the synthesis of SA and added a metabolic burden.
l-DOPA is a major drug for the treatment of Parkinson’s disease, and microbial enzymatic synthesis is an essential way for its industrial production. The expression of tyrosine phenol-lyase (TPL) derived from Erwinia herbicola under six different constitutive promoters in Escherichia coli was studied. The recombinant strain 5 can express TPL well with growth. The optimal medium composition of this strain was as follows: tryptone 18 g/L, yeast extract 28 g/L, glycerol 10 g/L. After the cell culture is completed, the collected cells were used to catalyze the production of l-DOPA, and the concentration can reach 67.9 g/L.
The gram-positive bacterium Bacillus licheniformis exhibits obvious selective utilization on carbon sources. This process is mainly governed by the global regulator catabolite control protein A (CcpA), which can recognize and bind to multiple target genes that are widely distributed in metabolic pathways. Although the DNA-binding domain of CcpA has been predicted, the influence of key amino acids on target gene recognition and binding has yet to be uncovered. In this study, the impact of Lys31, Ile42 and Leu56 on in vitro protein–DNA interactions and in vivo carbon source selective utilization was investigated. The results showed that alanine substitution of Lys31 and Ile42, located within the 3rd helices of the DNA-binding domain, significantly weakened the binding strength between CcpA and target genes. These mutations also lead to alleviated repression of xylose utilization in the presence of glucose. On the other hand, the Leu56Arg mutant in the 4th helices exhibited enhanced binding affinity compared with that of the wild-type one. When this mutant was used to replace the native one in B. licheniformis cells, the selective utilization of glucose over xylose increased. This study provides a new strategy for understanding the relationship between the function and structure of regulatory proteins. This study also used a new strategy was used to regulate carbon source utilization beyond CCR engineering.
Pinene is an active natural monoterpene from plants and has important applications in flavorings, fragrances,and pesticides. Especially, pinene dimers are regarded as renewable fuels with high density. However, the microbial pinene production was limited by the low activity pinene synthase. In this study, the pinene synthase activity was improved by fusion linker optimization and chaperon coexpression. To construct the pinene pathway in Saccharomyces cerevisiae, YPL062W gene was deleted to increase the MVA pathway precursor acetyl-CoA. Truncated 3-hydroxyl-3-methylglutaryl-CoA reductase (tHMG1), isopentenyl-diphosphate isomerase (IDI1), and farnesyl diphosphate synthase mutant (ERG20 F96W−N127W) were then integrated to improve the GPP pool. Pinene synthase tPt1 was expressed in the constructed engineered yeast, and the titer of pinene reached 0.166 mg/L. GPP is the direct precursor of pinene, ERG20 ww and tPt1 were fused by different linkers and orders to improve the accessibility of GPP. Pinene titer reached 9.94 mg/L by fusion these proteins in the order of ERG20 ww and tPt1 and with a flexible linker (G)8. After that, several chaperons were coexpressed and the chaperon Sil1p improved the pinene titer to 10.2 mg/L with a yield of 1.63 mg/L·OD600. The results presented here provide novel information on the applications of protein fusion and protein chaperons in microbial pinene production.