Molecular modification and biotechnological applications of microbial aspartic proteases

The growing preference for incorporating microbial aspartic proteases in industries is due to their high catalytic function and high degree of substrate selectivity. These properties, however, are attributable to molecular alterations in their structure and a variety of other characteristics. Molecular tools, functional genomics, and genome editing technologies coupled with other biotechnological approaches have aided in improving the potential of industrially important microbial proteases by addressing some of their major limitations, such as: low catalytic efficiency, low conversion rates, low thermostability, and less enzyme yield. However, the native folding within their full domain is dependent on a surrounding structure which challenges their functionality in substrate conversion, mainly due to their mutual interactions in the context of complex systems. Hence, manipulating their structure and controlling their expression systems could potentially produce enzymes with high selectivity and catalytic functions. The proteins produced by microbial aspartic proteases are industrially capable and far-reaching in regulating certain harmful distinctive industrial processes and the benefits of being eco-friendly. This review provides: an update on current trends and gaps in microbial protease biotechnology, exploring the relevant recombinant strategies and molecular technologies widely used in expression platforms for engineering microbial aspartic proteases, as well as their potential industrial and biotechnological applications.

Mulberry (Morus alba L.) leaf powder modified the processing of meat alternatives: Principal component analysis from apparent properties to chemical bonds

For texture control in plant-meat alternatives, the interrelationship between apparent characteristics and chemical bonds in high-fiber formulations remains unclear. The influence of mulberry leaf powder on apparent characteristics and chemical bonds of raw materials, block and strip products at addition amounts of 0.5-25% was analyzed. The results showed that 8% addition significantly increased the chewiness of the block by 98.12%. The strips' texture shows a downward trend, and the processing produced more redness and color difference. Additives promoted the formation of voids, lamellar and filamentous structures, and the strip produced more striped structures. Disulfide bonds significantly increased in the block, and the β-turn in the secondary structure enhanced by 12.20%. The β-turn transformed into a β-sheet in strips. Principal component analysis revealed that the texture improvement was associated with producing disulfide bonds and β-turn, providing a basis for high-fiber components to improve products' apparent characteristics by chemical bonds.

Long noncoding RNA transcriptome analysis reveals novel lncRNAs in Morus alba 'Yu-711' response to drought stress

Drought stress has been a key environmental factor affecting plant growth and development. The plant genome is capable of producing long noncoding RNAs (lncRNAs). To better understand white mulberry (Morus alba L.) drought response mechanism, we conducted a comparative transcriptome study comparing two treatments: drought-stressed (EG) and well-watered (CK) plants. A total of 674 differentially expressed lncRNAs (DElncRNAs) were identified. In addition, 782 differentially expressed messenger RNAs (DEmRNAs) were identified. We conducted Gene Ontology (GO) and KEGG enrichment analyses focusing on the differential lncRNAs cis-target genes. The target genes of the DElncRNAs were most significantly involved in the biosynthesis of secondary metabolites. Gene regulatory networks of the target genes involving DElncRNAs-mRNAs-DEmRNAs and DElncRNA-miRNA-DEmRNA were constructed. In the DElncRNAs-DEmRNAs network, 30 DEmRNAs involved in the biosynthesis of secondary metabolites are collocated with 46 DElncRNAs. The interaction between DElncRNAs and candidate genes was identified using LncTar. In summary, quantitative real-time polymerase chain reaction (qRT-PCR) validated nine candidate genes and seven target lncRNAs including those identified by LncTar. We predicted that the DElncRNAs-DEmRNAs might recruit microRNAs (miRNAs) to interact with gene regulatory networks under the drought stress response in mulberry. The findings will contribute to our understanding of the regulatory functions of lncRNAs under drought stress and will shed new light on the mulberry-drought stress interactions.

Silkworm pupae protein co-degradation by magnetic nanoparticles immobilized proteinase K and Mucor circinelloides aspartic protease for further utilization of sericulture by-products

Silkworm pupae, by-product of sericulture industry, is massively discarded. The degradation rate of silkworm pupae protein is critical to further employment, which reduces the impact of waste on the environment. Herein, magnetic Janus mesoporous silica nanoparticles immobilized proteinase K mutant T206M and Mucor circinelloides aspartic protease were employed in the co-degradation. The thermostability of T206M improved by enhancing structural rigidity (t1/2 by 30 min and T50 by 5 °C), prompting the degradation efficiency. At 65 °C and pH 7, degradation rate reached the highest of 61.7%, which improved by 26% compared with single free protease degradation. Besides, the immobilized protease is easy to separate and reuse, which maintains 50% activity after 10 recycles. Therefore, immobilized protease co-degradation was first applied to the development and utilization of silkworm pupae resulting in the release of promising antioxidant properties and reduces the environmental impact by utilizing a natural and renewable resource.

Dual promoter strategy enhances co-expression of α-L-rhamnosidase and enhanced fluorescent protein for whole-cell catalysis and bioresource valorization

Developing circular economy is the only way to improve the efficiency of resource utilization. Whole-cell catalysis is an effective method to recycle enzymes, improve catalytic efficiency, and reduce production costs. The enzyme, α-L-rhamnosidase has considerable application prospects in the field of biocatalysis as it can hydrolyze a variety of α-L rhamnoses. In the present study, the genes for α-L-rhamnosidase (rhaB1) and enhanced fluorescent protein (EGFP) were co-expressed using a bi-promoter expression vector pRSFDuet1 and their enzymatic properties were evaluated. To our knowledge, this study has established an effective rhamnosidase-fluorescent indicator and whole-cell catalytic system for the first time. Moreover, we analyzed the change in the activity of the crude rhaB1-EGFP as well as its whole-cell during the biocatalysis process using fluorescence intensity. Recombinant rhaB1-EGFP as a product which contains rhaB1 and EGFP showed higher thermal stability, pH stability, and conversion efficiency than rhaB1, and its optimum temperature for rutin catalysis was ideal for industrial applications. Moreover, under the optimal conditions of a rutin concentration of 0.05 g/L, pH of 6.0, temperature of 40 °C, a yield of 92.5% was obtained. Furthermore, we demonstrated the relationship between the fluorescence intensity and enzyme activity. This study established a highly efficient whole-cell catalytic system whose activity can be evaluated by fluorescence intensity, providing a reference for enzyme recycling.

Improvement in catalytic activity and thermostability of a GH10 xylanase and its synergistic degradation of biomass with cellulase

BACKGROUND

Xylanase is one of the most extensively used biocatalysts for biomass degradation. However, its low catalytic efficiency and poor thermostability limit its applications. Therefore, improving the properties of xylanases to enable synergistic degradation of lignocellulosic biomass with cellulase is of considerable significance in the field of bioenergy.

RESULTS

Using fragment replacement, we improved the catalytic performance and thermostability of a GH10 xylanase, XylE. Of the ten hybrid enzymes obtained, seven showed xylanase activity. Substitution of fragments, M3, M6, M9, and their combinations enhanced the catalytic efficiency (by 2.4- to fourfold) as well as the specific activity (by 1.2- to 3.3-fold) of XylE. The hybrids, XylE-M3, XylE-M3/M6, XylE-M3/M9, and XylE-M3/M6/M9, showed enhanced thermostability, as observed by the increase in the T ₅₀ (3-4.7 °C) and T _m (1.1-4.7 °C), and extended t _1/2 (by 1.8-2.3 h). In addition, the synergistic effect of the mutant xylanase and cellulase on the degradation of mulberry bark showed that treatment with both XylE-M3/M6 and cellulase exhibited the highest synergistic effect. In this case, the degree of synergy reached 1.3, and the reducing sugar production and dry matter reduction increased by 148% and 185%, respectively, compared to treatment with only cellulase.

CONCLUSIONS

This study provides a successful strategy to improve the catalytic properties and thermostability of enzymes. We identified several xylanase candidates for applications in bioenergy and biorefinery. Synergistic degradation experiments elucidated a possible mechanism of cellulase inhibition by xylan and xylo-oligomers.

Microfluidic tools for lipid production and modification: a review

Microfluidics has great potential as an efficient tool for a large range of applications in industry. The ability of such devices to deal with an extremely small amount of fluid has additional benefits, including superlatively fast and efficient mass and heat transfer. These characteristics of microfluidics have attracted an enormous amount of interest in their use as a novel tool for lipid production and modification. In addition, lipid resources have a close relationship with energy resources, and lipids are an alternative renewable energy source. Here, recent advances in the application of microfluidics for lipid production and modification, especially in the discovery, culturing, harvesting, separating, and monitoring of lipid-producing microorganisms, will be reviewed. Other applications of microfluidics, such as the modification of lipids from microorganisms, will also be discussed. The novel microfluidic tools in this review will be useful in applications to improve lipid production and modification in the future.

Prenatal androgen blockade accelerates pubertal development in male rhesus monkeys

Aspects of the prenatal environment, including steroid hormones, modulate the timing of puberty onset in many mammalian species. This study tested whether prenatal androgen manipulations altered pubertal development in male rhesus macaques (Macaca mulatta). Pregnant females received testosterone enanthate (TE), the androgen receptor blocker flutamide, or vehicle during one of two periods of gestation, and their male offspring were observed for morphological, endocrine, and behavioral development from 3 to 4.5 years of age. Males exposed to flutamide early in gestation had a greater response to exogenous GnRH prepubertally, and greater testes volume, elevated testosterone, and elevated LH at age 3.5 than did control subjects. Males exposed to flutamide late in gestation also had greater testes volumes at age 3.5 than did control males. However, these differences between flutamide treated males and control males did not persist postpubertally. By 4.5 years of age, development in control males had reached comparable levels to that of flutamide-treated males. Late gestation treatment with TE had no effect on morphological pubertal development but early TE treatment altered some aspects of endocrine function during puberty. None of the prenatal androgen manipulations affected sexual behavior. These findings suggest that prenatal androgens, in conjunction with social factors, masculinize pubertal timing in rhesus monkey males.

Timing of prenatal androgen exposure: anatomical and endocrine effects on juvenile male and female rhesus monkeys

Prenatal androgen shapes genital differentiation. In humans, genital anatomy determines sex of rearing and subsequent behavioral development. Rhesus monkey genital anatomy and neuroendocrine function are sexually differentiated, and behavioral development occurs in a complex social environment. We investigated prenatal hormonal influences on sexual differentiation by suppressing or increasing androgens in male and female rhesus monkeys. Pregnant multiparous female rhesus monkeys received 35-40 days of testosterone enanthate (TE) treatment, androgen antagonist (flutamide, FL) treatment, or vehicle starting on gestation day (GD) 35 or 40 (early) or GD 110 or 115 (late). Exogenous androgen increased neonatal LH secretion in females when given early and altered female genital differentiation when administered either early or late. TE treatment, early or late in gestation, had no measurable effects on male genital differentiation or neuroendocrine function. Early FL treatment, however, radically altered male genital differentiation, producing in two cases males with a urethral opening separate from the glans. In females, early FL treatment produced detectable alterations in genitalia consistent with a reduced exposure to prenatal androgen, suggesting that female rhesus monkeys are naturally exposed prenatally to meaningful levels of T. Late FL treatment reduced male penis size and increased neonatal T secretion, but had no effect in females. This is the first study to block endogenous prenatal testosterone in rhesus monkeys, thereby altering sexual differentiation. These findings illustrate the complexity of prenatal influences on anatomical and neuroendocrine development. The relationship between the anatomical changes reported here and sex differences in behavior is currently under investigation.

The role of queens in colonies of the swarm-founding wasp Parachartergus colobopterus

Social insect queens reproduce while workers generally do not. Queens may also have other behavioural roles in the colony. In small, independent-founding colonies of social wasps, the dominant queen physically enforces her interests over those of the workers and serves as a pacemaker of the colony, stimulating workers to forage and engage in other tasks. By contrast, in large-colony, swarm-founding wasps, the collective interests of the workers are fulfilled in sex allocation and production of males, whether or not they coincide with the interests of the queens. The behavioural role of the queens in such species has not been extensively studied. We investigated the role of the queens both in regulating worker activity and in reducing the numbers of reproductively active queens in the swarm-founding epiponine wasp Parachartergus colobopterus. We found no evidence that queens regulate worker activity, as they were rarely involved in any interactions. Worker activity may be self-organized, without centralized active control by anyone. Furthermore, we found no evidence that the reduction in queen number characteristic of this tribe of wasps occurs in response to aggression among queens. The reduction in queen number may be a result of worker treatment of queens, although worker discrimination against some queens was not obvious in our data. i Copyright 2000 The Association for the Study of Animal Behaviour.

Comparison of a neural network approach with five traditional methods for predicting creatinine clearance in patients with human immunodeficiency virus infection

STUDY OBJECTIVE

To compare the results of an artificial neural network approach with those of five published creatinine clearance (Cl(cr)) prediction equations and with the measured (true) Cl(cr) in patients infected with the human immunodeficiency virus (HIV).

DESIGN

Six-month prospective study.

SETTINGS

Two university medical centers.

PATIENTS

Sixty-five HIV-infected patients: 18 relatively healthy outpatients and 47 inpatients.

INTERVENTIONS

All subjects had urine collected for 24 hours to determine Cl(cr).

MEASUREMENTS AND MAIN RESULTS

The 16 input variables were age, ideal body weight, actual body weight, body surface area, height, and the following blood chemistries: sodium, potassium, aspartate aminotransferase, alanine aminotransferase, red blood cell count, platelet count, white blood cell count, glucose, serum creatinine, blood urea nitrogen, and albumin. The only output variable was Cl(cr). A training set of 55 subjects was used to develop the relationship between input variables and the output variable. The trained neural network was then used to predict Cl(cr) of a validation set of 10 subjects. Mean differences between predicted Cl(cr) and actual Cl(cr) (bias) were 4.1, 28.7, 29.4, 26.0, 31.8, and 55.8 ml/min/1.73 m2 for the artificial neural network, Cockcroft and Gault, Jelliffe 1, Jelliffe 2, Mawer et al, and Hull et al methods, respectively.

CONCLUSION

The accuracy of predicting Cl(cr) in subjects with HIV infection by the artificial neural network is superior to that of the five equations that are currently used in clinical settings.

Quantitative structure-pharmacokinetic relationships for systemic drug distribution kinetics not confined to a congeneric series

Many attempts have been made to describe quantitative structure-pharmacokinetic relationships within a congeneric series of drug molecules. The goal is to develop a predictive relationship that could predict in vivo results for other drugs within that series. These studies typically evaluate pharmacokinetic parameters that are reflective of both distribution and elimination processes. This work utilizes the results from 17 noncongeneric drugs reported in 18 pharmacokinetic studies. The objective was to determine if drug distribution parameters that were independent of elimination could be predicted from easily measured physicochemical parameters with a data base that included a wide variety of drugs that were not congeners of one another. Regression models utilizing a linear and a quadratic response surface were used to predict the various distribution parameters from physicochemical parameters, including molecular weight, intrinsic solubility, alcohol solubility, protein binding, and the distribution coefficient. Analogous to the extent of absorption, the extent of drug distribution can be predicted reasonably well by the probability that the drug will distribute into the peripheral system before being eliminated and by the volume of distribution at steady state. The duration of distribution, analogous to the rate of absorption, can be predicted by the mean transit time through the peripheral system the mean residence time of the drug in the peripheral system and the intrinsic mean residence time in the peripheral system. The ability to use statistical models to approximate drug distribution parameters without the constraints of working within a congeneric series provides some valuable opportunities.

Pharmacokinetics of morphine sulfate in patients with burns

Morphine sulfate (MS) pharmacokinetics was evaluated in seven patients with a mean body surface area burn of 21.5% to ascertain a rational basis for the management of pain in patients with burns. Treatments included a MS constant rate infusion followed by an oral MS solution (MS-OS) (5 to 15 mg administered every 3 hours) and then a 30 mg MS-controlled release tablet (MS-CR) every 8 hours. Each treatment was separated by a washout period when sampling of morphine was done. The apparent terminal half-life for MS-OS was 3 hours, which is similar to that of patients without burns, but the apparent terminal half-life for the MS-CR in patients with burns was substantially longer at 14.7 hours. The mean time to reach peak concentration for MS-CR was delayed relative to MS-OS 1.4 versus 0.5 hours, and the peak concentration was attenuated. The mean release time of the MS for the CR tablet is about 15 hours. The renal clearances of the MS-CR (114 ml/min) and MS-OS (147 ml/min) were less than the measured creatinine clearance (177 ml/min) but greater than the creatinine clearance (106 ml/min) predicted for a healthy individual. The prolonged release of MS-CR makes the MS-CR a good choice in the management of pain in patients with burns on an 8- to 12-hour dosing schedule, even though the patient might exhibit an increased clearance.

Effect of aspirin and sulindac on methotrexate clearance

The pharmacokinetics of low dose methotrexate (MTX) were evaluated in 12 rheumatoid arthritis patients in the presence and absence of steady-state levels of salicylic acid (ASA) and sulindac (SU). Using a Latin square design, patients were given MTX plus ASA (mean 3.4 g/day), MTX plus SU (mean 400 mg/day), or MTX alone. On a background of at least one year of regular MTX therapy, patients received 10 mg/m2 MTX iv (mean 17.8 mg) given after at least 2 weeks of treatment with each of the above regimens. Plasma concentrations of MTX and 7-hydroxymethotrexate (7-OH-MTX) were measured using HPLC. No differences in MTX clearance (Cl) were found comparing MTX alone, MTX + ASA, and MTX + SU. However, if one particular subject that had a very low clearance when receiving MTX alone was excluded, there was a statistically significant decrease in MTX clearance when either ASA or SUL were present. It is also noteworthy that ASA significantly increased the exposure of the subject to 7-OH-MTX and, to a lesser extent, so did sulindac. Since 7-OH-MTX has been shown to be an active metabolite when given for cytotoxic effects at higher doses and because it has been show to be nephrotoxic at doses a thousand-fold greater than used in rheumatoid arthritis, nonsteroidal anti-inflammatory drugs should be used cautiously with MTX until further large scale safety studies are conducted. The data indicate that if a clinically significant interaction were to occur, ASA is more likely than SU to interact with MTX.

Pharmacokinetics of low-dose methotrexate in rheumatoid arthritis patients

The pharmacokinetics and bioavailability of low-dose methotrexate (MTX) (10 mg/m2) were evaluated in 41 subjects who had definite or classical rheumatoid arthritis as defined by the American Rheumatism Association criteria. Subjects received 10 mg/m2 (to the nearest 2.5 mg) of MTX in a single oral dose and a single intravenous (iv) dose one week apart. Serum concentrations for this low-dose regimen were monitored using a radiochemical ligand binding assay. The results indicate the MTX is cleared from the plasma at a rate of 84.6 mL/min/m2. The terminal half-life was approximately 6 h. The volumes of distribution at steady state and for the central compartment were 22.2 and 13.5 L/m2, respectively. The mean residence time in the body, in the systemic circulation, and in the periphery were estimated to be 4.7, 3.0, and 1.7 h, respectively, with a peripheral single-pass mean transit time of 6.0 h and an intrinsic mean residence time in the periphery of 7.9 h. The mean absorption time was 1.2 h and the oral bioavailability was 0.70. The ratio of synovial fluid concentration to serum concentration 4 and 24 h after a dose was found to be approximately 1.0, indicating that at least within that time range serum and synovial fluid concentrations are approximately equal. Because of conflicting results and insufficient data from previous high-dose pharmacokinetic studies, it is difficult to say whether or not low-dose MTX pharmacokinetics differs from those of high-dose MTX.

Gold pharmacokinetics in breast milk and serum of a lactating woman

During 20 weeks of aurothioglucose therapy, gold in a mother's serum and breast milk and her nursing infant's serum and urine were measured. The mother's steady state plasma gold was 4.05 mg/l; it was 0.041 mg/l in breast milk. Only 0.0255 mg gold appeared in the breast milk/24 h. We calculated that only 0.1785 mg gold (0.71% of the weekly dose) would appear in the breast milk over a week. No gold (less than 5 X 10(-7) mg/l) was found in the infant's plasma or urine. It is very unlikely that more than minute amounts of gold are absorbed from the mother's breast milk when breast feeding an infant.

Drug therapy considerations in the elderly

The growing elderly population receives an increasing proportion of the prescriptions dispensed each year. There are a number of problems associated with drug therapy in the elderly. This article reviews some of the pharmacological factors, which may change with increasing age, including absorption, transportation, tissue localization, receptor sites, homeostasis, excretion and metabolism, and which in turn may alter the action of a drug. Suggestions are made regarding the treatment of elderly patients.