Fermentative intensity of L-lactic acid production using self-immobilized pelletized Rhizopus oryzae

L-Lactic acid is a promising three-carbon building-block chemical, widely used in the food, pharmaceutical, leather and textile industries and Rhizopus oryzae is an important filamentous fungus for the production of L-lactic acid with high optical purity. This study investigated the medium compositions for the maximum biomass cultivation of R. oryzae L-lactic acid fermentation, and optimized the operation parameters for semi-continuous repeated fermentation in a stirred tank fermentor using response surface method (RSM) analysis. The results indicated that a higher biomass cultivation of 3.750±0.05 g/L was achieved when the medium was composed of 12% (w/v) glucose, 0.4% (w/v) ammonium sulfate and 0.045% (w/v) monopotassium phosphate. The optimal fermentation conditions for the initial batch were as follows: the aeration was 0.75 L/(L·min), inoculation of germs was 11% and agitation speed was 560 rpm. The fermentative intensity of the initial batch and the sequentially repeated batches with self-immobilized pelletized R. oryzae were 2.162 g/(L·h) and 3.704 g/(L·h), respectively. Key words: Self-immobilized, Rhizopus oryzae, pellet, lactic acid, response surface method (RSM)

Effect of prodigiosin on the alleviation of the intestinal inflammation of weaned rats based on 1H-NMR spectroscopy study and biochemistry indexes

Weaning results in intestinal dysfunction, mucosal atrophy, transient anorexia, and intestinal barrier defects. In this study, the effect of prodigiosin (PG) on the intestinal inflammation of weaned rats was investigated by using 1 H-NMR spectroscopy and biochemistry indexes to regulate the intestinal metabolism. After administration for 14 days, the body mass of the PG group was increased by 1.29‑ and 1.26-fold compared with those of the control and alcohol groups, respectively, using a dose of 200 μg PG·kg-1 body weight per day. PG increased organic acid content and decreased moisture, pH values, and free ammonia in feces. In addition, PG alleviated the intestinal inflammation of weaned rats. The analysis of 1 H-NMR signal peak attribution and the model validation of metabolic data of feces contents showed that PG significantly affected the metabolism of small molecular compounds in the intestinal tract of weaned rats. This study presents the promising alternative of using PG to alleviate intestinal inflammation effectively in the intestinal tract of weaned rats

Recombinant Expression of Serratia marcescens Outer Membrane Phospholipase A (A1) in Pichia pastoris and Immobilization With Graphene Oxide-Based Fe3O4 Nanoparticles for Rapeseed Oil Degumming

Enzymatic degumming is an effective approach to produce nutritional, safe, and healthy refined oil. However, the high cost and low efficiency of phospholipase limit the application of enzymatic degumming. In this study, an 879 bp outer membrane phospholipase A (A1) (OM-PLA1) gene encoding 292 amino acid residues was isolated from the genome of Serratia marcescens. The recombinant OM-PLA1 profile of appropriately 33 KDa was expressed by the engineered Pichia pastoris GS115. The OM-PLA1 activity was 21.2 U/mL with the induction of 1 mM methanol for 72 h. The expression efficiencies of OM-PLA1 were 0.29 U/mL/h and 1.06 U/mL/OD600. A complex of magnetic graphene oxide (MGO) and OM-PLA1 (MGO-OM-PLA1) was prepared by immobilizing OM-PLA1 with graphene oxide-based Fe3O4 nanoparticles by cross-linking with glutaraldehyde. The content of phosphorus decreased to 5.1 mg/kg rapeseed oil from 55.6 mg/kg rapeseed oil with 0.02% MGO-OM-PLA1 (w/w) at 50°C for 4 h. MGO-OM-PLA1 retained 51.7% of the initial activity after 13 times of continuous recycling for the enzymatic degumming of rapeseed oil. This study provided an effective approach for the enzymatic degumming of crude vegetable oil by developing a novel phospholipase and improving the degumming technology

Effects of Three Hydrophilic Colloids on the Properties of Phosphorylated Surimi-Crab Meat Mixed Gels

The effects of adding different amounts (0.1%, 0.2%, 0.3%, 0.4% and 0.5%) of psyllium husk powder (PHP), gellan gum (GG) or konjac glucomannan (KGM) on the properties of phosphorylated surimi-crab meat mixed gels (MG) were investigated. The gel properties were improved by adding a small amount (0.1%) of PHP or GG. With increasing addition level of hydrophilic colloids, phase separation occurred, so that the gel properties did not significantly change and even began to decrease. However, the addition of KGM had no significant effect on the breaking force or gel strength, and no phase separation was observed under laser scanning confocal microscopy (LSCM). The addition of PHP and GG increased the temperature at which G’ began to decrease, which was beneficial to the improvement of gel properties. The denaturation of myosin required higher temperature and less energy in the phosphorylated MG system with hydrophilic colloids, and temperature may become a major influential factor in the denaturation process. The overall structural stability of proteins in MG was enhanced by adding a small amount of PHP or KGM. However, PHP and GG had a destructive effect on actin. On the contrary, the addition of a small amount of KGM could increase the structural stability of actin, which may be unfavorable for the formation of gels. The interaction between myosin and actin in the MG system was conducive to enhancing the overall structural stability of proteins. The three hydrophilic colloids, especially GG, at an addition level of 0.1% was beneficial to the improvement of gel properties. The incorporation of hydrophilic colloids may be a novel strategy to improve the quality of phosphorylated MG

Heterologous signal peptides-directing secretion of Streptomyces mobaraensis transglutaminase by Bacillus subtilis

Microbial transglutaminase (MTG) from Streptomyces mobaraensis has been widely used for crosslinking proteins in order to acquire products with improved properties. To improve the yield and enable a facile and efficient purification process, recombinant vectors, harboring various heterologous signal peptide-encoding fragments fused to the mtg gene, were constructed in Escherichia coli and then expressed in Bacillus subtilis. Signal peptides of both WapA and AmyQ (SP wapA and SP amyQ ) were able to direct the secretion of pre-pro-MTG into the medium. A constitutive promoter (P hpaII ) was used for the expression of SP wapA -mtg, while an inducible promoter (P lac ) was used for SP amyQ -mtg. After purification from the supernatant of the culture by immobilized metal affinity chromatography and proteolysis by trypsin, 63.0 ± 0.6 mg/L mature MTG was released, demonstrated to have 29.6 ± 0.9 U/mg enzymatic activity and shown to crosslink soy protein properly. This is the first report on secretion of S. mobaraensis MTG from B. subtilis, with similar enzymatic activities and yields to that produced from Escherichia coli, but enabling a much easier purification process

Effects of different cooking methods on the edible quality of crayfish (Procambarus clarkii) meat

The effect of steaming (100 ℃), boiling (100 ℃), frying (160 ℃) and high-pressure steam (121 ℃) on crayfish (Procambarus clarkii) quality was compared. The results showed that all four treatments have sterilization effect. The color, taste and texture of crayfish treated by steaming and boiling were better than by frying and high-pressure steam. Among the four cooking methods, the frying group has the highest cooking loss (32%) and thiobarbituric acid value (0.71 mg/kg). The effects of four thermal treatment on the content of astaxanthin of crayfish meat were significantly different. By comparing the content of volatile flavor compounds (VOCs), it was found that the crayfish treated by steaming and frying containing more species VOCs than the other two methods. For cooking crayfish, steaming could be beneficial for maintaining good edible quality. These results would be helpful for crayfish processing and new products development

The Effect of Salt on the Gelling Properties and Protein Phosphorylation of Surimi-Crabmeat Mixed Gels

The effects of different salt additions (1.0%, 1.5%, 2.0%, 2.5%, 3.0%, and 3.5%) on the gelling properties and protein phosphorylation of the mixed gels (MG) formed by silver carp (Hypophthalmichthys molitrix) surimi with 10% crabmeat were investigated. The MG’s breaking force, deformation, gel strength, and water-holding capacity (WHC) increased as the salt concentration increased. The intrinsic fluorescence intensity of the samples initially decreased and then increased, reaching the lowest when the NaCl concentration was 2.5%. The result of SDS–polyacrylamide gel electrophoresis indicated that large aggregates were formed by protein–protein interaction in the MG containing 2.5% or 3.0% NaCl, decreasing the protein band intensity. It was also found that with the addition of NaCl, the phosphorus content initially increased and then decreased, reaching the maximum when the NaCl concentration was 2% or 2.5%, which was similar to the changing trend of actin band intensity reported in the results of Western blot. These results revealed that the amount of salt used had a significant effect on the degree of phosphorylation of the MG protein. The increase in phosphorylation was linked to improved gelling properties, which could lead to new ideas for manufacturing low-salt surimi products in the future

CRISPR-Cas9 Approach Constructed Engineered <i>Saccharomyces cerevisiae</i> with the Deletion of <i>GPD2</i>, <i>FPS1</i>, and <i>ADH2</i> to Enhance the Production of Ethanol

Bioethanol plays an important value in renewable liquid fuel. The excessive accumulation of glycerol and organic acids caused the decrease of ethanol content in the process of industrial ethanol production. In this study, the CRISPR-Cas9 approach was used to construct S. cerevisiae engineering strains by the deletion of GPD2, FPS1, and ADH2 for the improvement of ethanol production. RNA sequencing and transcriptome analysis were used to investigate the effect of gene deletion on gene expression. The results indicated that engineered S. cerevisiae SCGFA by the simultaneous deletion of GPD2, FPS1, and ADH2 produced 23.1 g/L ethanol, which increased by 0.18% in comparison with the wild-type strain with 50 g/L of glucose as substrate. SCGFA strain exhibited the ethanol conversion rate of 0.462 g per g of glucose. In addition, the contents of glycerol, lactic acid, acetic acid, and succinic acid in SCGFA decreased by 22.7, 12.7, 8.1, 19.9, and 20.7% compared with the wild-type strain, respectively. The up-regulated gene enrichment showed glycolysis, fatty acid, and carbon metabolism could affect the ethanol production of SCGFA according to the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. Therefore, the engineering strain SCGFA had great potential in the production of bioethanol

Comparison of the nutritional qualities of the pond, rice-field and wild crayfish (Procambarus clarkii) meat

The meat yield, and chemical and nutrients composition of the pond, rice-field and wild-caught crayfish meat were investigated. The results showed that the meat yield of pond crayfish (10.52%) was significantly higher than that of rice-field (10.05%) and wild-caught (10.32%) crayfish. The rice-field crayfish meat had the highest moisture contents (81.43%) and the lowest protein content (15.50%). The higher lipid contents were found in the rice-field and pond crayfish meat (1.10% and 1.19%, respectively). While, the pond crayfish meat had the highest essential amino acids (6.09 g/100 g) and total amino acids (16.21 g/100 g) content, and the Σn-3/Σn-6 PUFA ratio (1.78). The essential amino acid index in the pond and rice-field crayfish meat was higher than 70 which indicated that they were high-quality protein. The pond crayfish meat contained more macro-minerals, but less micro-minerals. While, the trace minerals were rich in the rice-field crayfish meat. The heavy metals contents in the crayfish meat were under limit. Overall, the pond, rice-field and wild-caught crayfish meat all exhibited good nutritional quality, and the pond crayfish meat showed better in terms of amino acids and fatty acids composition. For the rice-field crayfish, most of its nutritional quality were similar with the wild-caught crayfish