Project description:Gene expression was studied at the periphery, an intermediate zone, and the centre of wild-type and ∆flbA colonies using Affymetrix A. niger whole genome microarrays. We used Affymetrix GeneChip A. niger Geome Arrays and identifed up- and down-regulated genes that may account for the differences between wild-type and ΔflbA colonies.
Project description:Guar gum consists mainly of galactomannan, and constitutes the endosperm of guar seeds that acts as a reserve polysaccharide for germination. Due to its molecular structure and physical properties, this biopolymer has been considered as one of the most important and widely used gums in industry. However, for many of these applications this (hemi-)cellulosic structure needs to be modified or (partially) depolymerized in order to customize and improve its physicochemical properties. In this study, transcriptome was employed to decipher the complete enzymatic arsenal for guar gum depolymerization by Aspergillus niger.
Project description:The food enzyme glucose oxidase (?-d-glucose:oxygen 1-oxidoreductase; EC 1.1.3.4) is produced with a genetically modified Aspergillus niger strain ZGL by DSM Food Specialties B.V.. The genetic modifications do not give rise to safety concerns. The food enzyme is free from viable cells of the production organism and recombinant DNA. The glucose oxidase is intended to be used in baking processes. Based on the maximum use levels, dietary exposure to the food enzyme-total organic solids (TOS) was estimated to be up to 0.004 mg TOS/kg body weight (bw) per day. The toxicity studies were carried out with an asparaginase from A. niger (strain ASP). The Panel considered this enzyme as a suitable substitute to be used in the toxicological studies, because they derive from the same recipient strain, the location of the inserts are comparable, no partial inserts were present and the production methods are essentially the same. Genotoxicity tests did not raise a safety concern. The systemic toxicity was assessed by means of a repeated dose 90-day oral toxicity study in rats. The Panel identified a no observed adverse effect level (NOAEL) at the highest dose of 1,038 and 1,194 mg TOS/kg bw per day (for males and females, respectively) that, compared with the estimated dietary exposure, results in a sufficiently high margin of exposure (MoE) (of at least 260,000). Similarity of the amino acid sequence to those of known allergens was searched and one match was found. The Panel considered that, under the intended conditions of use, the risk of allergic sensitisation and elicitation reactions by dietary exposure cannot be excluded, but the likelihood to occur is considered to be low. Based on the data provided, the Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.
Project description:The food enzyme triacylglycerol lipase (triacylglycerol acylhydrolase, EC 3.1.1.3) is produced with a genetically modified Aspergillus niger strain LFS by DSM Food Specialties B.V.. The genetic modifications do not give rise to safety concerns. The food enzyme is free from viable cells of the production organism and recombinant DNA. The triacylglycerol lipase food enzyme is intended to be used in baking processes. Based on the maximum use levels, dietary exposure to the food enzyme-total organic solids (TOS) was estimated to be up to 0.020 mg TOS/kg body weight (bw) per day. The toxicity studies were carried out with an asparaginase from A. niger (strain ASP). The Panel considered this enzyme as a suitable substitute to be used in the toxicological studies, because they derive from the same recipient strain, the location of the inserts are comparable, no partial inserts were present and the production methods are essentially the same. Genotoxicity tests did not raise a safety concern. The systemic toxicity was assessed by means of a repeated dose 90-day oral toxicity study in rats. The Panel identified a no observed adverse effect level (NOAEL) at the highest dose of 1,038 and 1,194 mg TOS/kg bw per day (for males and females, respectively) that, compared with the estimated dietary exposure, results in a sufficiently high margin of exposure (MoE) (of at least 51,900). Similarity of the amino acid sequence to those of known allergens was searched and no match was found. The Panel considered that, under the intended conditions of use, the risk of allergic sensitisation and elicitation reactions by dietary exposure cannot be excluded, but the likelihood to occur is considered to be low. Based on the data provided, the Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.
Project description:Ochratoxin A (OTA) is a mycotoxin that can contaminate a wide range of crops such as grains and grapes. In this study, a novel fungal mutant strain (FS-UV-21) with a high OTA degradation rate (74.5%) was obtained from Aspergillus niger irradiated with ultraviolet light (15 W for 20 min). The effect of pH, temperature, and inoculation concentration on the degradation of OTA by FS-UV-21 was investigated, and the results revealed that the detoxification effect was optimal (89.4%) at a pH of 8 and a temperature of 30 °C. Ultra-performance liquid chromatography-tandem mass spectrometry was used to characterize the degraded products of OTA, and the main degraded product was ochratoxin α. Triple quadrupole-linear ion trap-mass spectrometry combined with LightSight software was used to analyze the biotransformation pathway of OTA in FS-UV-21, to trace the degraded products, and to identify the main metabolite, P1 (C19H18ClNO6, m/z 404). After the FS-UV-21 strain was treated with OTA, the HepG2 cellular toxicity of the degradation products was significantly reduced. For the real sample, FS-UV-21 was used to remove OTA from wheat bran contaminated by mycotoxins through fermentation, resulting in the degradation of 59.8% of OTA in wheat bran. Therefore, FS-UV-21 can be applied to the degradation of OTA in agricultural products and food.
Project description:Itaconic acid is a value-added organic acid that is widely applied in industrial production. It can be converted from citric acid by some microorganisms including Aspergillus terreus and Aspergillus niger. Because of high citric acid production (more than 200 g/L), A. niger strains may be developed into powerful itaconic acid-producing microbial cell factories. In this study, industrial citric acid-producing strain A. niger YX-1217, capable of producing 180.0-200.0 g/L, was modified to produce itaconic acid by metabolic engineering. A key gene cadA encoding aconitase was expressed in A. niger YX-1217 under the control of three different promoters. Analyses showed that the PglaA promoter resulted in higher levels of gene expression than the PpkiA and PgpdA promoters. Moreover, the synthesis pathway of itaconic acid was extended by introducing the acoA gene, and the cadA gene, encoding aconitate decarboxylase, into A. niger YX-1217 under the function of the two rigid short-peptide linkers L1 or L2. The resulting recombinant strains L-1 and L-2 were induced to produce itaconic acid in fed-batch fermentations under three-stage control of agitation speed. After fermentation for 104 h, itaconic acid concentrations in the recombinant strain L-2 culture reached 7.2 g/L, which represented a 71.4% increase in itaconic acid concentration compared with strain Z-17 that only expresses cadA. Therefore, co-expression of acoA and cadA resulted in an extension of the citric acid metabolic pathway to the itaconic acid metabolic pathway, thereby increasing the production of itaconic acid by A. niger.
Project description:BackgroundStarch is one of the most important renewable polysaccharides in nature for production of bio-ethanol. The starch saccharification step facilitates the depolymerization of starch to yield glucose for biofuels production. The filamentous fungus Aspergillus niger (A. niger) is the most used microbial cell factory for production of the commercial glucoamylase. However, the role of each component in glucoamylases cocktail of A. niger O1 for starch saccharification remains unclear except glucoamylase.ResultsIn this study, we identified the key enzymes contributing to the starch saccharification process are glucoamylase, α-amylase and acid α-amylase out of 29 glycoside hydrolases from the 6-day fermentation products of A. niger O1. Through the synergistic study of the multienzymes for the starch saccharification in vitro, we found that increasing the amount of α-amylase by 5-10 times enhanced the efficiency of starch saccharification by 14.2-23.2%. Overexpression of acid α-amylase in strain O1 in vivo increased the total glucoamylase activity of O1 cultures by 15.0%.ConclusionsOur study clarifies the synergistic effects among the components of glucoamylases cocktail, and provides an effective approach to optimize the profile of saccharifying enzymes of strain O1 for improving the total glucoamylase activity.
Project description:The food enzyme alpha-amylase (4-α-d-glucan glucanohydrolase; EC 3.2.1.1) is produced with a non-genetically modified Aspergillus niger (strain DP-Azb60) by Danisco US Inc. The food enzyme is free from viable cells of the production organism. The α-amylase is intended to be used in baking processes. Based on the maximum use levels, dietary exposure to the food enzyme-total organic solids (TOS) was estimated to be up to 0.503 mg TOS/kg body weight (bw) per day. Genotoxicity tests with the food enzyme did not indicate a genotoxic concern. The systemic toxicity was assessed by means of a repeated dose 90-day oral toxicity study in rats. The Panel identified a no-observed-adverse-effect level (NOAEL) at the highest dose of 1,000 mg TOS/kg bw per day that, compared with the estimated dietary exposure, results in a sufficiently high margin of exposure (of at least 1,988). Similarity of the amino acid sequence to those of known allergens was searched and one match was found to Asp o 21, an alpha-amylase from Aspergillus oryzae. The Panel considered that, under the intended conditions of use, the risk of allergic sensitisation and elicitation reactions upon dietary exposure to this food enzyme cannot be excluded, but the likelihood is considered low. Based on the data provided, the Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.
Project description:The food enzyme glucoamylase (glucan 1,4-?-glucosidase; EC 3.2.1.3) is produced with the genetically modified strain of Aspergillus niger by Novozymes A/S. The genetic modifications do not give rise to safety concerns. The food enzyme is free from viable cells of the production organism and recombinant DNA. This glucoamylase is intended to be used in brewing processes and in starch processing for glucose syrups production. Residual amounts of total organic solids (TOS) are removed by the purification steps applied during the production of glucose syrups, consequently dietary exposure was not calculated. For brewing processes, based on the proposed maximum use levels, dietary exposure to the food enzyme-TOS was estimated to be below 3.627 mg TOS/kg body weight (bw) per day in European populations. Genotoxicity tests did not raise a safety concern. The systemic toxicity was assessed by means of a repeated dose 90-day oral toxicity study in rodents. The Panel identified a no-observed-adverse-effect level (NOAEL) at the highest dose of 1,360 mg TOS/kg bw per day. Similarity of the amino acid sequence to those of known allergens was searched and one match was found. The Panel considered that, under the intended condition of use, the risk of allergic sensitisation and elicitation reactions upon dietary exposure to this food enzyme cannot be excluded, but the likelihood of such reactions to occur is considered to be low. Based on the data provided, the removal of TOS during the production of glucose syrups and the derived margin of exposure for brewing processes, the Panel concluded that this food enzyme does not raise safety concerns under the intended conditions of use.