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Bacterial cellulose (BC) holds several unique properties such as high water retention capability, flexibility, biocompatibility, and high absorption capacity. All these features make it a potential material for wound healing applications. However, it lacks antibacterial properties, which hampers its applications for infectious wound healings. This study reported BC-based dressings containing ε-polylysine (ε-PL), cross-linked by a biocompatible and mussel-inspired polydopamine (PDA) for promoting infectious wound healing. BC membranes were coated with PDA by a simple self-polymerization process, followed by treating with different contents of ε-PL. The resulted membranes showed strong antibacterial properties against tested bacteria by both in vitro and in vivo evaluations. The membranes also exhibited hemocompatibility and cytocompatibility by in vitro investigations. Moreover, the functionalized membranes promoted infected wound healing using Sprague-Dawley rats as a model animal. A complete wound healing was observed in the group treated with functionalized membranes, while wounds were still open for control and pure BC groups in the same duration. Histological investigations indicated that the thickness of newborn skin was greater and smoother in the groups treated with modified membranes in comparison to neat BC or control groups. These results revealed that the functionalized membranes have great potential as a dressing material for infected wounds in future clinical applications.

Komagataeibacter xylinus has received increasing attention as an important microorganism for the conversion of several carbon sources to bacterial cellulose (BC). However, BC productivity has been impeded by the lack of efficient genetic engineering techniques. In this study, a lambda Red and FLP/FRT-mediated site-specific recombination system was successfully established in Komagataeibacter xylinus . Using this system, the membrane bound gene gcd , a gene that encodes glucose dehydrogenase, was knocked out to reduce the modification of glucose to gluconic acid. The engineered strain could not produce any gluconic acid and presented a decreased bacterial cellulose (BC) production due to its restricted glucose utilization. To address this problem, the gene of glucose facilitator protein ( glf ; ZMO0366) was introduced into the knockout strain coupled with the overexpression of the endogenous glucokinase gene ( glk ). The BC yield of the resultant strain increased by 63.63-173.68%, thus reducing the production cost.

Esters are important flavor compounds in alcoholic beverages. Although they are present at trace levels, esters play a key role in the formation of flavors, especially fruity flavors, in beverages. Low ester contents result in bland beer and unpleasant flavor. In this study, three recombinant strains, ethanol O-acyltransferase encoding EEB1 overexpression strain (31194:: EEB1), 2-enoyl thioester reductase encoding ETR1 overexpression strain (31194:: ETR1), and EEB1- ETR1 co-overexpression strain (31194:: EEB1:: ETR1), were constructed. Ethyl hexanoate production by 31194:: EEB1 and 31194:: EEB1:: ETR1 was 106% higher than that by the parental strain. Further, ethyl octanoate production by 31194:: EEB1 and 31194:: EEB1:: ETR1 was enhanced by 47 and 41%, respectively, compared with that of parental strain 31194. However, no difference was observed between 31194:: ETR1 and the parental strain in terms of ethyl hexanoate and ethyl octanoate production. This indicates that although EEB1 overexpression in Saccharomyces pastorianus enhanced ethyl hexanoate and ethyl octanoate production, ETR1 expression levels did not affect the extracellular concentrations of these esters.

To explore the regulatory factor of light quality affecting exopolysaccharide (EPS) production, transcriptome analysis of Nostoc flagelliforme cells exposed to red light (R), blue light (B), and mixed light (B/R = 15:7) (BR) with white fluorescent light as control was performed. The differentially expressed genes mainly enriched in carbohydrate metabolism and energy metabolism. Significant enrichment in the oxidation-reduction process and energy metabolism indicated that intracellular redox homeostasis was disrupted. An assay of reactive oxygen species (ROS) and malondialdehyde contents demonstrated light quality induced oxidative stress. To illustrate the relationship between ROS level and EPS accumulation, the effects of the exogenous addition of ROS scavenger N-acetyl cysteine and inducer H 2 O 2 on the oxidation-reduction level and EPS production were compared. The results revealed that light quality regulated EPS biosynthesis via the intracellular ROS level directly other than oxidative stress. Understanding such relationships might provide guidance for efficient EPS production to regulate the intracellular redox level.

ε-Poly-L-lysine (ε-PL), a naturally occurring amino acid homopolymer, has been widely used as a food preservative. However, its antimicrobial mechanism has not been fully understood. This study investigated the antimicrobial mode of action of ε-PL on a yeast, Saccharomyces cerevisiae. When treated with ε-PL at the concentration of 500 μg/mL, cell mortality was close to 100% and the phospholipid bilayer curvature, pores, and micelles on the surface of S. cerevisiae were clearly observed by scanning electron microscopy (SEM). At the level of 200 μg/mL, ε-PL significantly inhibited the cell growth of S. cerevisiae. When treated with 50 μg/mL ε-PL, the yeast cell was able to grow but the cell cycle was prolonged. A significant increase in cell membrane permeability was induced by ε-PL at higher concentrations. Metabolomics analysis revealed that the ε-PL stress led to the inhibition of primary metabolic pathways through the suppression of the tricarboxylic acid cycle and glycolysis. It is therefore proposed that the microbiostatic effect of ε-PL at lower levels on S. cerevisiae is achieved by inducing intracellular metabolic imbalance via disruption of cell membrane functions. Moreover, the results suggested that the antimicrobial mechanism of ε-PL on S. cerevisiae can in fact change from microbiostatic to microbicidal when the concentration of ε-PL increased, and the mechanisms of these two modes of action were completely different.

Plant-based proteins are valuable supplements to compensate the gap between supply and demand in the food or feed industry. However, they lack essential amino acids, such as lysine in cereal grains and sulfur-containing amino acids in legumes, which greatly limit their wider uses for human and animals. In this study, the contents of nutritional ingredients and antinutritional factors of Caragana korshinskii Kom. and its protein isolates were quantitatively investigated. It was shown that the crude protein contents of C. korshinskii Kom. and its protein isolates obtained by alkaline extraction method (Al-CPI) and acetone precipitation method (A-CPI) were 9.1, 50.1, and 42.6%, respectively. Amino acid contents in C. korshinskii Kom., Al-CPI, and A-CPI basically exceeded the FAO/WHO (2007) reference pattern for adults except sulfur-containing amino acids. The lysine levels in C. korshinskii Kom., Al-CPI, and A-CPI were 4.1, 3.1, and 3.8 mg/100 mg crude protein respectively, which were higher than some other kinds of cereal grains. The methionine in A-CPI (1.39 mg/100 mg crude protein) was even higher than that in soybean. The antinutritional factors in C. korshinskii Kom. and Al-CPI were generally lower than those in some other kinds of legumes except total phenol and tannin. Total phenol and tannins in Al-CPI were 19.02 and 5.66 mg/g dry substance, respectively, but they were undetectable in A-CPI. This study provided a detailed analysis on nutritional and antinutritional factors in C. korshinskii Kom. and its protein isolates, indicating that they have a great potential on food and feed additives.

Seeking cheap, sustainable protein sources greatly facilitates in alleviating the dependence upon expensive animal-based protein in many developing countries. Caragana korshinskii Kom. offers a good alternative feedstock because of its high-content of protein, low fertilizer and pesticide requirements, excellent stress (high salty and less water) tolerance, wide adaptability, etc. The functional properties of C. korshinskii Kom. protein isolates by three different extraction methods were investigated. The extraction processes greatly influenced the physiological characteristics of protein isolates. C. korshinskii Kom. protein isolate by traditional alkaline extraction (Al-CPI) exhibited good performance on emulsifying activity index, oil and water absorption capacity, and foaming property compared to A-CPI ( C. korshinskii Kom. protein isolate by the acetone precipitation method) and TCA-CPI ( C. korshinskii Kom. protein isolate by trichloroacetic acid-acetone precipitation). The water and oil adsorption capacities of Al-CPI were observed at 4.99 and 3.45 g/g, respectively, even much higher than those of soy protein isolate (SPI) (3.94 and 2.95 g/g, respectively). The highest foaming capacity was observed by Al-CPI at 185.0%, followed by A-CPI (177.5%), TCA-CPI (142.5%), and SPI (141.9%), respectively. It has to be noted that A-CPI showed good solubility at acidic pH and excellent in vitro digestibility. After sequential pepsin-trypsin digestion, the percentage of N release of A-CPI reached up to 83.7%, which was 1.63 times that of Al-CPI (51.2%), 1.19 times that of TCA-CPI (70.1%), and slightly higher than that of the commercial SPI (82.5%). These results indicate that C. korshinskii Kom. holds great potential for application in the animal feed and food additive industry.

Some approaches for improving recombinant phenylalanine ammonia lyase (PAL) stability in Escherichia coli during the enzymatic methods of l-phenylalanine (l-Phe) production were developed following preliminary studies by means of statistical-based experiment designs (response surface method). The traditional non-statistical technology was used to screen four critical factors for PAL stability during the bioconversion process, viz., glycerin, sucrose, 1,4-dithiothreitol (DTT), and MgSO(4). The central composite design (CCD) was applied to optimize the combined effect of critical factors for recombinant PAL stability and understand the relationship between the factors and PAL stability. The optimum values for testing variables were 13.04 mM glycerin, 1.87 mM sucrose, 4.09 mM DTT, and 69 mM Mg(2+). A second-order model equation was suggested and then validated experimentally. The model adequacy was very satisfactory because the coefficient of determination was 0.88. The maximum PAL activity was retained as 67.73 units/g after three successive cycles of bioconversion. In comparison to initial PAL activity, the loss of PAL activity was only 22%. PAL activity was enhanced about 23% in comparison to the control (without any stabilizer additives). PAL stability was significantly improved during successive bioconversion. The results obtained here verified the effectiveness of the applied methodology and may be helpful for l-Phe production on an industrial scale.