Latex peptidases of Calotropis procera for dehairing of leather as an alternative to environmentally toxic sodium sulfide treatment

Enzymatic processes for animal hide/skin collagen fiber purification processing: Recent progress, challenges and recommendations

Collagen fiber purification is the most important pretreatment process in the recycling of animal hide/skin, by-products of meat production, and can be utilized to produce value-added materials. Traditional animal hide/skin resource utilization technologies face serious challenges in the aspect of production efficiency and environmental sustainability. Enzymatic collagen fiber purification processing is thought to be one of the most promising technologies that can minimize the use of chemicals and energy, reduce CO2-eq emissions, and achieve sustainable development of animal hide/skin reutilization. However, enzymatic processes have not been well accepted for industrial-scale applications in factories so far. In this review, recent progress and challenges of enzymatic collagen fiber purification processing were comprehensively overviewed in the aspect of the key mechanisms and technologies of enzyme application. Recommendations for the direction of enzyme selection and development were put forward, which is expected to pave the way for the industrial-scale application of enzymes in animal hide/skin collagen fiber purification processing.

Traditional knowledge of wild plants on traditional tools, materials, products and economic practices in southern Yemen

BACKGROUND

The traditional knowledge in southern Yemen is rich in wild medicinal and food plants, which has been documented in our previous studies. In addition, other significant and general traditional usage for the daily livelihood requirements of local people (beyond medicinal and food plant uses) has not been studied before and needs urgent documentation.

METHODS

Ethnobotanical data on of wild plants used by local people in southern Yemen were collected by oral questionnaire interviews. Most informants (n = 1020) were local elderly from 15 different localities in southern Yemen. The local names and non-medicinal and non-food uses of plants were identified and analyzed.

RESULTS

The ethnobotanical data resulted various traditional uses of 73 plant species distributed in 28 families. The most represented families were Fabaceae, Asteraceae and Malvaceae. The most growth forms were trees and shrubs. Seven main and common categories of traditional uses were determined and classified as handicraft, health aids, livestock husbandry and beekeeping, economic and commercial plant products, agriculture tools, construction timber and fuel. The most cited species were identified for Ziziphus spina-christi, Vachellia tortilis, Vachellia nilotica, Anisotes trisulcus, Dracaena hanningtonii (Sansevieria ehrenbergii) and Aerva javanica, which have multi-purpose values of traditional usage. Nine major traditional uses of local wild plants were recorded: handicraft, agriculture tools, products aid general health, economic products, construction timber, livestock husbandry, bee keeping, fuel and ornamental.

CONCLUSIONS

Despite the challenges on local traditional knowledge of wild plants, it still requested vital to many usages of traditional life and still have an economic value and heritage required of develop the daily livelihood level of the local people especially in rural areas. This includes the traditional uses of wild plants in handicraft skills, tools of agriculture, constructions. The importance of the continuity of traditional industries and their transmission to generations lies in the local population's reliance on local natural resources without relying on external resources in situations such as wars. This is the first study that contributes to documenting and analyzing the indigenous knowledge on traditional general usage of wild plants in southern Yemen.

Autoproteolysis of Procerain and Procerain B mediated by structural changes

Procerain (Pc) and Procerain B (PcB) are two latex proteases from Calotropis procera having potential applications in food and other industries. However, autolytic degradation of these proteases limits their potential use in industry. Nevertheless, basic mechanism underlying the autoproteolysis has not been detailed. In order to understand the same, we subjected the enzymes to various denaturing and activating conditions. The results showed that structural changes induced by different denaturing conditions trigger their autoproteolysis. We also observed differential response of Pc, PcB and other papain-like proteases towards autocatalysis in presence of reducing agent in-spite of sharing the same structural fold, including the number of disulfide bonds. The possible reason underlying this intriguing observation is also discussed. Further, present work establishes that structural changes in the proteases lead to autoproteolysis and the enzymes are stable unless they experience structural perturbation. These findings could thus be useful for their practical applications in industries.

Production of Plant Proteases and New Biotechnological Applications: An Updated Review

An updated review of emerging plant proteases with potential biotechnological application is presented. Plant proteases show comparable or even greater performance than animal or microbial proteases for by-product valorization through hydrolysis for, for example, cheese whey, bird feathers, collagen, keratinous materials, gelatin, fish protein, and soy protein. Active biopeptides can be obtained as high added value products, which have shown numerous beneficial effects on human health. Plant proteases can also be used for wastewater treatment. The production of new plant proteases is encouraged for the following advantages: low cost of isolation using simple procedures, remarkable stability over a wide range of operating conditions (temperature, pH, salinity, and organic solvents), substantial affinity to a broad variety of substrates, and possibility of immobilization. Vegetable proteases have enormous application potential for the valorization of industrial waste and its conversion into products with high added value through low-cost processes.

A review on phytochemical constituents and pharmacological potential of Calotropis procera

Calotropis procera is locally known as Aak or Madar in Hindi, milk weed in English and belongs to the family Apocynaceae and subfamily Asclepiadoideae. Although a wasteland plant, it is of sacred use as its flowers are offered for worshipping Lord Shiva, a Hindu God. Tribes all over the world use the plant in treatment of various diseases like snake bite, body pain, asthma, epilepsy, cancer, sexual disorders, skin diseases and many more. This plant contains various phytoconstituents such as flavonoids, terpenoids, cardenolides, steroids oxypregnanes etc. Though literature searches reveal many reviews about ethnomedicinal uses, chemical composition and pharmacological activities, no recent papers are available that provide an overview of the therapeutic potential and toxicity of Calotropis procera. Hence, the insight of this review is to provide a systemic summary of phytochemistry, pharmacology, toxicology and therapeutic potential of Calotropis procera and to highlight the gaps in the knowledge so as to offer inspiration for future research.

Calotropis procera is also known as Aak or Madar. The present review provides a systematic outline of phytochemistry, toxicology, pharmacology and therapeutic potential of Calotropis procera.

Development and validation of a label-free method for measuring the collagen hydrolytic activity of protease

Collagen is the most abundant fibrous structural protein, and therefore, the quantitative evaluation of the effect of protease on collagen has a profound influence on enzyme application. In this research, unlabeled native bovine hide powder was utilized to detect collagen hydrolytic activity of the protease. The optimum conditions of the determination method were as follows: 30 mg/mL substrate concentration, 30 min reaction time, and 2-9 U/mL enzyme concentration. Then, several typical industrial protease preparations were chosen to measure collagenolytic activities at different temperatures and pH values, whose change trends were quite distinct from those of proteolytic activity assay method based on casein or dye-labeled hide powder substrate. Especially, in the pH 5-7, casein hydrolytic activities of these proteases showed sharper peaks with relative activity from 6% to 100%, whereas, their collagen hydrolytic activities based on native hide powder exhibited 30-100% with broader peaks. And collagen hydrolytic activities resulted from using dye-labeled substrate reached a lower optimum pH value than that of other methods. Besides, the results of these measurements displayed a moderate degree of reproducibility. This method is more reasonable than the protease assay method using casein or labeled hide powder as the substrate in many fields.

Insights into substrate specificity of proteases for screening efficient dehairing enzymes

Though numerous proteases have been isolated and screened for the dehairing purpose, their use in the leather industry is limited mainly due to high cost, the need for expertise, and control during unit operation and alterations in the quality of leather due to lack of the right kind of substrate specificity of the enzymes used. This paper deals with the comparative specificity and dehairing efficiency of proteases isolated from Bacillus cereus VITSP01 (PE2) and Brevibacterium luteolum VITSP02 (PE). PE2 and PE were found to be trypsin-like and elastase-like serine proteases respectively. The protease of VITSP02 degraded the proteoglycans efficiently in comparison to that of VITSP01. The results suggest that the possible targets of the studied proteases might be skin proteoglycans, including those cementing the hair root bulb. Hence, an in-depth study on the substrate specificity of the dehairing proteases would help in designing an improved screening method for isolating potent dehairing enzymes.

An Overview of the Characteristics and Potential of Calotropis procera From Botanical, Ecological, and Economic Perspectives

Calotropis procera (Aiton) Dryand. (commonly known as the apple of sodom, calotrope, and giant milkweed) is an evergreen, perennial shrub of the family Apocynaceae, mainly found in arid and semi-arid regions. It is a multipurpose plant, which can be utilized for medicine, fodder, and fuel purposes, timber and fiber production, phytoremediation, and synthesis of nanoparticles. It has been widely used in traditional medicinal systems across North Africa, Middle East Asia, and South-East Asia. At present, it is being extensively explored for its potential pharmacological applications. Several reports also suggest its prospects in the food, textile, and paper industries. Besides, C. procera has also been acknowledged as an ornamental species. High pharmacological potential and socio-economic value have led to the pantropical introduction of the plant. Morpho-physiological adaptations and the ability to tolerate various abiotic stresses enabled its naturalization beyond the introduced areas. Now, it is recognized as an obnoxious environmental weed in several parts of the world. Its unnatural expansion has been witnessed in the regions of South America, the Caribbean Islands, Australia, the Hawaiian Islands, Mexico, Seychelles, and several Pacific Islands. In Australia, nearly 3.7 million hectares of drier areas, including rangelands and Savannahs, have been invaded by the plant. In this review, multiple aspects of C. procera have been discussed including its general characteristics, current and potential uses, and invasive tendencies. The objectives of this review are a) to compile the information available in the literature on C. procera, to make it accessible for future research, b) to enlist together its potential applications being investigated in different fields, and c) to acknowledge C. procera as an emerging invasive species of arid and semi-arid regions.

Standardized production of a homogeneous latex enzyme source overcoming seasonality and microenvironmental variables

Calotropis procera produces a milky sap containing proteolytic enzymes. At low concentrations, they induce milk-clotting (60 µg/ml) and to dehair hides (0.05 and 0.1%). A protocol for obtaining the enzymes is reported. The latex was mixed with distilled water and the mixture was cleaned through centrifugation. It was dialyzed with distilled water and centrifuged again to recover the soluble fraction [EP]. The dialyze is a key feature of the process. EP was characterized in terms of protein profile, chemical stability, among other criteria. Wild plants belonging to ten geographic regions and grown in different ecological conditions were used as latex source. Collections were carried out, spaced at three-month, according to the seasons at the site of the study. Proteolytic activity was measured as an internal marker and for determining stability of the samples. EP was also analyzed for metal content and microbiology. EP showed similar magnitude of proteolysis, chromatographic and electrophoretic profiles of proteins. Samples stored at 25 °C exhibited reduced solubility (11%) and proteolytic capacity (11%) after six months. Enzyme autolysis was negligible. Microbiological and metal analyses revealed standard quality of all the samples tested. EP induced milk clotting and hide dehairing after storage for up to six months.

Influence of galactosidases on glycosaminoglycan removal Vis-à-Vis opening up of skin matrix to enable complete rehydration

Enzymatic interventions in animal skin processing are increasingly being considered as safe and benign technology options due to the reduction and replacement of potential harmful chemicals. In this study, galactosidases have been employed for rehydration of preserved skins and hides to improve the process efficiency and minimize hazardous sodium sulfide. The purpose of rehydration is to ensure the skin is hydrated uniformly to facilitate subsequent physico-chemical processes of leather making. Improper rehydration leads to reduction in the quality and value of the leather. The efficacy of the enzymatic process was studied using histological images and scanning electron microscopic analysis. Pollution load changes and the extent of carbohydrate removal were also quantified. The study indicates possibility for substantial reduction in process duration and water input (up to 30%) during rehydration of preserved animal skins when galactosidases are used as rehydration aid without affecting the quality of the leather. Thus use of galactosidases in rehydration ensures uniform accelerated rehydration and provides significant environmental benefits to tanning industry, by reducing harmful substances in subsequent operations.

Identification, characterization, and antifungal activity of cysteine peptidases from Calotropis procera latex

Cysteine peptidases (EC 3.4.22) are the most abundant enzymes in latex fluids. However, their physiological functions are still poorly understood, mainly related to defense against phytopathogens. The present study reports the cDNA cloning and sequencing of five undescribed cysteine peptidases from Calotropis procera (Aiton) Dryand (Apocynaceae) as well as some in silico analyses. Of these, three cysteine peptidases (CpCP1, CpCP2, and CpCP3) were purified. Their enzymatic kinetics were determined and they were assayed for their efficacy in inhibiting the hyphal growth of phytopathogenic fungi. The mechanism of action was investigated by fluorescence and atomic force microscopy as well as by induction of reactive oxygen species (ROS). The deduced amino acid sequences showed similar biochemical characteristics and high sequence homology with several other papain-like cysteine peptidases. Three-dimensional models showed two typical cysteine peptidase domains (L and R domains), forming a "V-shaped" active site containing the catalytic triad (Cys, His, and Asn). Proteolysis of CpCP1 was higher at pH 7.0, whereas for CpCP2 and CpCP3 it was higher at 7.5. All peptidases exhibited optimum activity at 35 °C and followed Michaelis-Menten kinetics. However, the major difference among them was that CpCP1 exhibited highest V_max, K_m, K_cat and catalytic efficiency. All peptidases were deleterious to the two fungi tested, with IC₅₀ of around 50 μg/mL. The peptidases promoted membrane permeabilization, morphological changes with leakage of cellular content, and induction of ROS in F. oxysporum spores. These results corroborate the hypothesis that latex cysteine peptidases play a role in defense against fungi.

Proteolytic extracts of three Bromeliaceae species as eco-compatible tools for leather industry

Most tanneries use high proportions of Na₂S and CaO during the dehairing step, resulting in effluents of high alkalinity and large amounts of suspended solid, besides the risk of liberating the toxic H₂S. Solid waste rich in protein is another environmental problem of tanneries. Enzymes are an interesting technological tool for industry due to their biodegradability, nontoxic nature, and nonpolluting effluent generation. In the leather industry, proteases have been chosen as a promising eco-friendly alternative to Na₂S/CaO dehairing. Extracts with high proteolytic activity have been obtained from fruits of Bromeliaceae species: Bromelia balansae Mez (Bb), Bromelia hieronymi Mez (Bh), and Pseudananas macrodontes (Morr.) Harms (Pm). In this work, Bb, Bh, and Pm have been studied for application in the leather industry, focusing in their dehairing properties. Enzymatic activities were measured against collagen, keratin, elastin, and epidermis while a dehairing assay was performed by employing cowhide. All extracts showed similar activity on collagen and epidermis, while Bh and Pm were the most active against keratin at the same caseinolytic unit (CU) values; Bh was the only extract active against elastin. Bb (1 CU/ml), Bh (1.5 CU/ml), and Pm (0.5 CU/ml) were able to depilate cowhide. Desirable characteristics of dehairing were observed for all extracts since hair pores did not show residual hair, grain surface was clean and intact, and collagen fiber bundles of dermis were not damaged. In conclusion, results here presented show that proteolytic extracts of Bromeliaceae species are promising eco-compatible tools for leather industry.