Evidences suggest that the homeostasis of gut microbiota is among the most important factors for maintaining the physical and mental health of the host. Among the multiple factors affecting the homeostasis of gut microbiota, diet is one of the decisive factors. Bioactive peptides derived from protein hydrolyzed by protease or fermented by microorganism have many physiological activities that their parent proteins do not have. Currently, bioactive peptides attract more and more attention due to their bidirectional interaction with gut microbes. It has been reported that some bioactive peptides could alter the composition of gut microbiota by influencing the intestinal microenvironment. Meanwhile, quite a few bioactive peptides that are released by gut microbes or intestinal cells could resist the pathogenic bacteria to sustain the homeostasis of gut microbiota. In this review, some exogenous bioactive peptides derived from food and some endogenous bioactive peptides released from intestinal cells or microbes were discussed to summary their effects on the modulation of gut microbiota. This review is expected to provide new ideas for related research, and as well to promote the application of bioactive peptides in the fields of food and medicine.
The rapid industrial and economic development runs on fossil fuel and other energy sources. Limited oil reserves, environmental issues, and high transportation costs lead towards carbon unbiased renewable and sustainable fuel. Compared to other carbon-based fuels, biodiesel is attracted worldwide as a biofuel for the reduction of global dependence on fossil fuels and the greenhouse effect. During biodiesel production, approximately 10% of glycerol is formed in the transesterification process in a biodiesel plant. The ditching of crude glycerol is important as it contains salt, free fatty acids, and methanol that cause contamination of soil and creates environmental challenges for researchers. However, the excessive cost of crude glycerol refining and market capacity encourage the biodiesel industries for developing a new idea for utilising and produced extra sources of income and treat biodiesel waste. This review focuses on the significance of crude glycerol in the value-added utilisation and conversion to bioethanol by a fermentation process and describes the opportunities of glycerol in various applications.
D-amino acids, different from the ubiquitous L-amino acids, are recognized as the “unnatural” amino acids. The applications of D-amino acids have drawn increasing interest from researchers in recent years, and D-amino acids are widely used in various industries, including for food products, pharmaceuticals, and agricultural chemicals. Inspired by the prevalent applications, many synthetic methods for D-amino acids have been developed, which are mainly divided into chemical synthetic methods and biosynthetic methods. Chemical synthesis of D-amino acids has a variety of disadvantages such as multiple reaction steps, low yields, low reaction rates, and difficulties in product extraction. Thus, biosynthetic methods utilizing enzymes are attracting increasing attention because they are more energy-saving and environmentally friendly compared to traditional chemical synthesis. Among all enzymatic methods, multi-enzymatic cascade catalytic methods have significant advantages, such as lower costs, no need for intermediate separation, and higher catalytic efficiency, which is ascribed to the spatial proximity of biocatalysts. In this review, advances in multi-enzyme cascade catalytic systems as well as chemo-enzymatic approaches to synthesize D-amino acids are discussed.
Microalgae are unicellular photosynthetic organisms that have been recently attracted potential interests and have applications in food, nutraceuticals, pharmaceuticals, animal feed, cosmetics, and biofertilizers industry. Microalgae are rich in a variety of high-value bioactive compounds which have potential benefits on human health and can be used for the prevention and curing of many disease conditions. But scale-up and safety issues remain a major challenge in the commercialization of microalgal products in a cost-effective manner. However, techniques have been developed to overcome these challenges and successfully selling the products derived from microalgae as food, cosmetics and pharmaceutical industries. Microalgae are rich in many nutrients and can be used for the production of functional food and nutraceuticals, safety and regulatory issues are major concerns and extensive research is still needed to make microalgae a commercial success in the future. Many practical difficulties are involved in making the microalgal food industry commercially viable. The present review focuses on the industrial applications of microalgae and the challenges faced during commercial production.
Bioelectrochemical systems (BESs) are a new and emerging technology in the field of fermentation technology. Electrical energy was provided externally to the microbial electrolysis cells (MECs) to generate hydrogen or value-added chemicals, including caustic, formic acid, acetic acid, and peroxide. Also, BES was designed to recover nutrients, metals or remove recalcitrant compounds. The variety of naturally existing microorganisms and enzymes act as a biocatalyst to induce potential differences amid the electrodes. BESs can be performed with non-catalyzed electrodes (both anode and cathode) under favorable circumstances, unlike conventional fuel cells. In recent years, value-added chemical producing microbial electrosynthesis (MES) technology has intensely broadened the prospect for BES. An additional strategy includes the introduction of innovative technologies that help with the manufacturing of alternative materials for electrode preparation, ion-exchange membranes, and pioneering designs. Because of this, BES is emerging as a promising technology. This article deliberates recent signs of progress in BESs so far, focusing on their diverse applications beyond electricity generation and resulting performance.
Ectoine is a high-value stabilizer and protective agent with various applications in enzyme industry, cosmetics, and biomedicine. In this study, rational engineering strategies have been implemented in Escherichia coli to efficiently produce ectoine. First, the synthetic pathway of ectoine was constructed in E. coli MG1655 by introducing an artificial thermal switch system harboring the ectABC cluster from Halomonas elongate, and the resulting strain produced 1.95 g/L ectoine. Second, crr encoding the glucose-specific enzyme II domain A of phosphotransferase system and iclR encoding the glyoxylate shunt transcriptional repressor were deleted in E. coli for enhancing the oxaloacetate supply, leading to the increasement of the ectoine titer to 9.09 g/L. Third, thrA encoding the bifunctional aspartokinase/homoserine dehydrogenase was removed from the genome to weaken the competitive pathway; simultaneously, an endogenous feedback-resistant lysC was overexpressed to complement the enzymatic activity deficiency of the aspartate kinase, leading to 30.36% increase of ectoine titer. Next, the expression of phosphoenolpyruvate carboxylase was modulated with varying gradient strength promoters to accelerate the biosynthesis efficiency of ectoine. Finally, aspDH encoding aspartate dehydrogenase from Pseudomonas aeruginosa PAO1 was overexpressed to further improve the biosynthesis of ectoine. The final strain MWZ003/pFT28-ectABC-EclysC*-aspDH-ppc3 produced 30.37 g/L ectoine after 36-h fed-batch fermentation with a yield of 0.132 g/g glucose and a productivity of 0.844 g/(L h).
The aim of this work was to study the pyocyanin pigment from Pseudomonas aeruginosa DN9. The work involves optimization of process parameters for enhanced production of pyocyanin pigment under submerged fermentation condition. During optimization process, maximum pyocyanin production (92.12 µg/ml) was obtained with carbon source mannitole, nitrogen source peptone, inorganic salt NaCl and metal ion FeSO4. Plackett Burman design and Response Surface Methodology (RSM) showed peptone, NaCl and KH2PO4 are significant variable in the production of pyocyanin pigment. The FTIR and GC–MS study was done to evaluate structural properties of pyocyanin pigment. The purified pigment was further analyzed as colouring agent and for inhibitory action against pathogenic microorganisms. Thus, present study showed Pseudomonas aeruginosa DN9 as promising culture for pigment production with potential biotechnological application.
The study was conducted to investigate the effect of sludge retention on bacterial community composition of membrane bioreactor (MBR) treating synthetic hospital wastewater. The removal of four pharmaceuticals, namely carbamazepine, estradiol, venlafaxine, and ibuprofen in MBR, was studied at varying sludge retention time (SRT) duration of 100, 45, and 15 days and hydraulic retention time (HRT) of 18 h. The removal of ibuprofen and estradiol was constant at varying SRT; however, a negligible removal of carbamazepine and low removal of venlafaxine was observed (< 20%). The study suggested that the SRT of 45 days in MBR could provide maximum treatment efficiency via decreasing membrane clogging. The effect of sludge age and pharmaceutical presence on the bacterial community was investigated via high-throughput sequencing. The study reveals that the variation in SRT affects the dynamics of the bacterial community significantly. For instance, the dominant bacterium Caldimonas of SRT 100 was disappeared at lower SRTs. Moreover, the profile of the dominant genus of the SRTs varied greatly from each other.
Non-specific electrostatics is crucial for structure and stability; recently, it has been argued that psychrophilic proteins may also utilize specific electrostatic interactions. Do psychrophilic proteins increase the number of salt bridges for cold adaptation? Are there any changes that occur in their sequence, which helps them to adapt in an extreme environment? Do intra-protein interactions affect their stability? Is there any special type of intra-protein interaction present in psychrophilic protein structure? This study will give all those answers. Sequences (n ~ 100) and structures of psychrophilic isocitrate dehydrogenase and mesophilic isocitrate dehydrogenase extracted from databases. Sequences had been analyzed in BLOCK and non-BLOCK format. The sequences of psychrophiles and mesophiles create two separate clades. The number of charged and uncharged polar residues is very much high in psychrophilic proteins. The formation of long network aromatic–aromatic interactions and network aromatic–sulfur interactions are very crucial for psychrophilic protein stability. Identification of these types of interactions is also a novelty of this study. Favorable mutation of charged residues with high-energy contributions affects the protein stability. This study will help in protein engineering.
Unconventional alternatives such as aerobic and anaerobic effluent from starch industry contain essential nutrients for Btk active ingredient synthesis. Effluent from starch industry is rich in carbon and nitrogen and can replace expensive feedstock used during the fermentation process.
The main objective of this study was to achieve a biopesticide formulation from starch industry wastewater (SIW) with high entomotoxicity (UI/ml) of larvae comparable to Foray 76B, which is a commercial biopesticide.
Bacillus thuringiensis var kurstaki HD1 (Btk) strain was cultivated and sub-cultured to aerobic, anaerobic digested effluent and SIW. Pre-treatment was carried on these different substrates to enhance the residual carbon required for Btk growth and delta endotoxin synthesis. After 48 hours of fermentation, cells count and delta-endotoxin were determined. A biopesticide formulation containing fermented broth and adjuvants was fed to larvae to determine larvae mortality.
Btk cell growth and sporulation profile in SIW media displayed a high total cell count and viable spores compared to btk growth in anaerobic or aerobic media after 48h fermentation. The maximum endotoxin concentration in the SIW medium was 435μg/mL, whereas, in anaerobic and aerobic effluent, the maximum concentrations were at 161 μg/mL and 136 μg/mL, respectively. When acidic treatment was performed at pH 2 for these substrates, entomotoxicity obtained from aerobic and anaerobic biopesticide formulations displayed significantly higher entomoxicity than the untreated ones. The entomotoxicity of SIW treated at pH 2 was equivalent to the standard Foray 76B which is 20,000 IU/μL.
Anaerobic and aerobic effluent did not contain enough total organic carbon to augment Btk growth and entomotoxicity. Substrates pre-treated at pH 2 provided significant organic matter for Btk growth and resulted in larval mortality equivalent to the com ercial biopesticide Foray 76B.