Degree Of Biodegradation Research Articles

Characterization of heavy oils from the Campos Basin, Brazil: Free biomarkers in oils, adsorbed and occluded in asphaltene structures

The Campos Basin is considered an important Brazilian petroleum province, with the most of its oils consisting in a mixture of biodegraded and non-biodegraded oils, which is related to more than one generation and migration pulse coupled with biodegradation events during successive stages of reservoir filling. Its turbidites reservoirs are also structural controlled through faults generated by halokinesis comprising the main route of oil migration from underlying source rocks. Throughout the biomarkers analyses of free hydrocarbons in oil, adsorbed, and occluded in the asphaltene structures, samples from different oilfields, and distances from the main fault responsible for its reservoirs filling, were comprehensive studied. The gas chromatography coupled mass spectrometer (GC-MS) methodology was applied. The results of biodegradation, source, and thermal maturation parameters reveals that the free and adsorbed saturated hydrocarbons are similarly altered, but differ in biodegradation degrees and pathways between oils, while occluded hydrocarbons and all fractions of aromatic compounds are well preserved. The predominance of biodegradation process over the recharge is suggested for distant samples from the main fault in each area, contributing to the local models of oil migration. The occluded hydrocarbons showed source similarities regardless of oilfield. According to thermal maturity based on unaltered aromatics compounds, the occluded hydrocarbons showed lower mature ratios than those free. This study introduces the application and limitations concerning biodegradation, source, and thermal maturation inferences from occluded hydrocarbons in asphaltenes covering Brazilian oils, in view to improve a concise geochemical tool in petroleum exploration.

Attempt to Extend the Shelf-Life of Fish Products by Means of Innovative Double-Layer Active Biodegradable Films.

In this study, we aimed to produce, innovative and, at the same time, environmentally-friendly, biopolymer double-layer films with fish processing waste and active lingonberry extract as additives. These double-layered films were based on furcellaran (FUR) (1st layer) and carboxymethyl cellulose (CMC) with a gelatin hydrolysate (HGEL) (2nd layer). The aim of the study was to assess their impact on the durability of perishable salmon fillets during storage, and to evaluate their degree of biodegradation. The fillets were analyzed for changes in microbiological quality (total microbial count, yeast and molds, and psychrotrophic bacteria), biogenic amine content (HPLC), and lipid oxidation (peroxidase and acid values, TBARS). The degree of biodegradation includes analysis of film and compost chemical composition solubility, respiratory activity, and ecotoxicity testing. The obtained results allow to suggest that active films are not only bacteriostatic, but even bactericidal when they used to coat fish fillets. Concerning the group of samples covered with the double-layer films, a 19.42% lower total bacteria count was noted compared to the control samples. Furthermore, it can be observed that the applied double-layer films have a potentially strong inhibitory effect on the accumulation of biogenic amines in fish, which is correlated with its antimicrobial effect (the total biogenic amine content for control samples totaled 263.51 mg/kg, while for the double-layer samples, their value equaled: 164.90 mg/kg). The achieved results indicate a high biodegradation potential, however, a too low pH of the film results in limiting seed germination and growth. Despite that, of these, double-layer films are a technology that has applicative potential.

Behaviour of modified epoxyurethanes reinforced with hemp wood core under accelerated weathering and soil burial test

Si-containing organic-inorganic epoxyurethane biocomposites were obtained. BPA type (Bisphenol A based) epoxy resin, used for synthesis of polymer matrix, was partially or completely replaced with epoxidized soybean oil (ESO). High amount (60 and 70 wt%) of hemp wood core (HWC) that is natural filler was used. Such materials may find potential application as plates or other pressed materials for building industry. To predict the behaviour of biocomposites under outdoor conditions during their operation period and after its expiration the samples were subjected to accelerated weathering and soil burial test respectively. The results of visual observation, measurements of weight, thickness, and flexural strength as well as thermogravimetric analysis (TGA) before and after exposure in a climate chamber evidenced that investigated biocomposites are stable to weathering. Particularly, values of gain in weight and thickness of the weathered samples were up to 2.9% and 1.9% respectively (with the lowest of them for the ones with maximum ESO content). The values of flexural strength of weathered ESO-modified composites were even by 13.4–32.0% higher than those of the unweathered ones. Such a phenomenon is mostly attributed to the reactions of post-curing promoted by high temperature and humidity applied during accelerated weathering. The results of soil burial test showed that the degree of biodegradation was directly proportional to the amount of ESO in biocomposites. Notably, after 1 year of soil exposure the weight loss was the lowest for biocomposite without ESO (30.1%), while it was the highest for biocomposite with maximum amount of ESO (44.5%).

Geochemical Investigation of the Cretaceous Crude Oil Reservoirs and Source Rock Samples in One of the Abadan Plain Oilfields, SW Iran

AbstractCrude oil and source rock samples from one of the main oilfields of the Abadan Plain, Zagros, Iran were analyzed geochemically. Rock‐Eval pyrolysis was conducted on Kazhdumi (Upper Cretaceous) and Gadvan (Lower Cretaceous) formations, which are the probable source rocks for the oil in the region. The results indicated that the Kazhdumi Formation can be classified as a fair‐to‐excellent source rock, while the Gadvan Formation can be identified as having poor‐to‐good source rock in the basin. Based on the cross‐plots of HI versus OI and S2 versus TOC, types II and III kerogen were identified from studied source samples in the area. Determination of the main fraction percentages of the Sarvak and Fahliyan crude oils represented that the oils from the Sarvak reservoir are paraffinic‐naphthenic and aromatic‐intermediate, whilst that from the Fahliyan reservoir is paraffinic and paraffinic‐naphthenic. Biomarker ratios of the saturated fractions of oil from both reservoirs indicate that the source rocks formed in reducing marine environments with carbonate‐shale lithology. Furthermore, biomarker data helped to distinguish the degree of biodegradation in the studied oils. According to geochemical analysis, oil samples from the Fahliyan reservoir were generated at a higher thermal maturity than the Sarvak reservoir samples.

Organic geochemical characteristics of sediments in the natural gas hydrate geo-system in Shenhu area, South China Sea

The Shenhu area of the South China Sea is one of the leading areas for natural gas hydrate investigation and exploitation in China. In this study, total organic carbon (TOC) content, total nitrogen (TN) content, and gas chromatographic-mass spectrometric (GC–MS) analysis of the soluble organic matter of sediments from sites W01B, W02B, and W03B were completed to understand the characteristics of organic matter in the sedimentary system with gas hydrates and provide theoretical support for further exploration in this area. Source indicators such as δ13Corg, TAR, and C21-/C21+ revealed that sites W01B and W02B have similar provenance characteristics in vertical profiles, with an increase of terrestrial source in the hydrate occurrence layers, while site W03B shows a gradual increase in marine source contribution as depth decreases. The asymmetric erosion and lateral deposition of the channel-levee depositional system are considered the controlling factors for the discrepancies in provenance indexes among the three sites. Analysis of the different source indicators revealed that the different kinds of soluble organic matter were subjected to varying degrees of biodegradation, and the distribution characteristics of n-alkanes were preferentially altered. Furthermore, it is found that biodegradations at sites W01B and W02B were more pronounced, particularly in hydrate occurrence layers. All of the microbial degradation indexes increase simultaneously and are consistent with the vertical distribution of hydrates, showing a similar triangular distribution trend. The increase in squalane, a characteristic compound representing methanogens, indicates that microbial degradation and methanogenesis are synchronized in the hydrate occurrence horizon, providing sufficient microbial gases for gas hydrates formation.

Development of a layered bacterial nanocellulose-PHBV composite for food packaging.

Most of the current materials used in food packaging are synthetic and non-degradable, raising environmental issues derived from the accumulation of plastics in landfills/waterways. The food industry increasingly needs eco-friendly sustainable materials that meet food-packaging requirements. Bacterial nanocellulose (BNC), a biopolymer obtained by fermentation, offers very good mechanical properties and the ability to carry and deliver active substances. However, its water-vapor permeability is too high for food-packaging applications. In this work, a layered biodegradable composite based on BNC and polyhydroxyalkanoate (PHBV) was produced, attempting to improve its overall barrier properties. Polyhydroxyalkanoate is a biopolymer with high degree of hydrophobicity and biodegradability, and is also obtained by fermentation. Wet BNC membranes produced by static culture were plasticized by impregnation of solutions of either glycerol (BNCgly ) or polyethylene glycol (MW 600) (BNCPEG ). The plasticized BNC was then coated with PHBV solution dissolved in formic acid, and oven dried at 148 °C. Overall, PHBV coating on plasticized BNC reduced water vapor permeability significantly (from 0.990 to 0.032 g.μm.m-2 .day-1 .Pa-1 ) under 50% relative humidity. It increased the hydrophobicity (contact angle from 10-40° to 80-90°) but decreased the stiffness (from 3.1GPa to 1.3 Gpa) of the composite. Overall, the mechanical and barrier properties of the layered composite obtained were considered suitable for food-packaging applications. The plasticizing (with glycerol or polyethylene glycol) of BNC significantly improved the mechanical performance and the PHBV coating reduced the water affinity (vapor and liquid state) on BNC. © 2022 Society of Chemical Industry.

Oil-source correlation under the complex geological conditions: A case study of the Chaiwopu Sag, southern Junggar Basin, NW China

Slightly (PM 1) to very strongly (PM 9) biodegraded crude oil was discovered in the reservoir of the Tashikula Formation in the eastern Chaiwopu Sag. The origin of oil in the eastern Chaiwopu Sag remains unclear due to different degrees of biodegradation and multi-stage nappe structure. In this study, the geochemical data from crude oil, source rocks and hydrocarbon inclusions are used to establish the correlations between oils and source rocks under complex geological conditions. The characteristics of biomarkers, isotopes and hydrocarbon inclusions reveal two stages of hydrocarbon charging in the eastern Chaiwopu Sag. Hydrocarbons formed during the first charging stage has low maturity and a relatively light carbon isotope composition, and its relative abundance of C 20-23 tricyclic terpanes follows the sequence: C 23 > C 21 > C 20 . Hydrocarbons formed during the second charging stage is characterized by relatively high maturity and heavy carbon isotope composition, and the corresponding abundance of C 20-23 tricyclic terpanes is C 23 < C 21 < C 20 . The biomarkers and isotopic characteristics of crude oil, source rocks and hydrocarbon inclusions reveal the hydrocarbons formed during the first charging stage originated from the Lucaogou Formation in the northern Chaiwopu Sag and the northern Bogeda Mountains, and those formed during the second charging stage originated from the Lucaogou Formation in the central Chaiwopu Sag. The high-quality source rocks and reservoirs of the Lucaogou Formation were deposited in the northern Chaiwopu Sag, which has great potential for tight/shale oil exploration. • The geochemical characteristics of potential source rocks in different regions are revealed. • Degradation grade of oils in the southeastern Chaiwopu Sag are revealed. • Reveal the maturity and accumulation stage of petroleum through the characteristics of hydrocarbon inclusions. • Reveal the origin of petroleum under complex geological conditions through biomarkers, isotopes and hydrocarbon inclusions.

Rapid profiling of carboxylic acids in reservoir biodegraded crude oils using gas purge microsyringe extraction coupled to comprehensive two-dimensional gas chromatography-mass spectrometry

Carboxylic acids (CAs) are important molecular markers in petroleum geochemistry, which can indicate the origin, migration and biodegradation of oils. In this work, an easy and fast method was developed for the separation and analysis of CAs in crude oils by the combination of gas purge microsyringe extraction (GP-MSE) and comprehensive two-dimensional gas chromatography-mass spectrometry (GC × GC–MS). CAs in oils were firstly reacted with a silylation reagent to improve their volatility and thermal stability. The silylated CAs were then separated from oils together with light hydrocarbons with GP-MSE treatment at a relatively low temperature (200 °C). Subsequently, direct analysis of the extract solutions by GC × GC–MS was performed. Profited from the extremely high peak capacity of GC × GC, the signals of silylated CAs could be easily distinguished from hydrocarbon signals. Under optimal conditions, the extraction time and the solvent consumption of GP-MSE were 8 min and 150 μL, respectively. In the analysis of reservoir crude oils with different biodegradation degrees, abundant CA signals were successfully detected, and the contents of CAs were found to vary regularly with the biodegradation degree.

Geochemical characteristics and origins of biodegraded oils in the Bongor Basin (Chad) and their implications for petroleum exploration

The Bongor Basin is a typical lacustrine passive-rifted basin situated in the West and Central African Rift System (WCARS). It has experienced two phases of tectonic inversion and features a complex process of petroleum generation and accumulation. A total of 41 crude oil samples from the basin were geochemically analyzed to investigate their compositions of molecular markers. The results show that the oils have similar origins and are likely to belong to the same oil population. However, there are significant differences in geochemical characteristics and physical properties, caused by the secondary alteration. The relative contents and distribution patterns of normal alkanes and acyclic isoprenoids indicate that some of the oils have suffered biodegradation to varying degrees. The samples can be divided into three categories according to their relative degrees of degradation: normal oil, slightly biodegraded oil (PM 1–3), and severely biodegraded oil (PM 5–7). The burial depth of oil reservoirs in this area is the predominant factor impacting on the level of biodegradation. Crude oils in reservoirs with burial depths of less than 800 m are all severely biodegraded, while oils in reservoirs with burial depths greater than 1300 m have experienced no evident biodegradation. In reservoirs with burial depths between 800 m and 1300 m, the biodegradation degrees vary from normal to severely biodegraded. Oil reservoirs with burial depths less than 1300 m and adjacent to major faults are readily subject to biodegradation, while reservoirs with similar burial depths, but a certain distance away from major faults, have suffered no evident biodegradation. Moreover, if primary reservoirs have been modified by tectonic activity after accumulation, the crude oils are more likely to be biodegraded. Faulted anticline traps may create more favorable geological conditions for preservation of crude oil than reverse extrusion anticline reservoirs. This study may provide practical guidance for the assessment and prediction of oil quality in future oil exploration.

Different metabolic pathways involved in anthracene biodegradation by Brevibacillus, Pseudomonas and Methylocystis Species

BackgroundPolycyclic aromatic hydrocarbons (PAHs) such as anthracene are one of the most toxic contaminants to our environment. Microbial biodegradation of these xenobiotics is a cost-effective technological solution. The present study aimed to recover some bacterial isolates from Beni-Suef Governorate in Egypt with high capabilities of anthracene biodegradation. The selected isolates were molecularly characterized by 16S rRNA gene sequencing, the degree of anthracene biodegradation was monitored using optical density (OD) and high-performance liquid chromatography (HPLC), PCR amplification of some selected genes encoding biodegradation of PAHs was monitored, and gas chromatography–mass spectrometry (GC–MS) analysis was applied for detecting the resulted metabolites.ResultThree bacterial isolates were studied, the 16s rRNA sequences of the isolates showed homology of the first isolate to Brevibacillus sp. (94.58 %), the second isolates showed homology to Pseudomonas sp. (94.53%) and the third isolate showed homology to Methylocystis sp. (99.61 %), all isolates showed the ability to degrade anthracene. PCR amplification of some selected genes encoding biodegradation of PAHs revealed the presence of many biodegrading genes in the selected strains. Gas chromatography-mass spectrometry (GC–MS) analysis of the metabolites resulted from anthracene biodegradation in the present study suggested that more than one biodegradation pathway was followed by the selected isolates.ConclusionsThe selected strains could represent a potential bioremediation tool in solving the PAHs problem in the Egyptian environment with a clean and cost-effective technique.Graphical

Evaluation of the Effectiveness of the Biopreparation in Combination with the Polymer γ-PGA for the Biodegradation of Petroleum Contaminants in Soil.

Biodegradation is a method of effectively removing petroleum hydrocarbons from the natural environment. This research focuses on the biodegradation of aliphatic hydrocarbons, monoaromatic hydrocarbons such as benzene, toluene, ethylbenzene, and all three xylene isomers (BTEX) and polycyclic aromatic hydrocarbons (PAHs) as a result of soil inoculation with a biopreparation A1 based on autochthonous microorganisms and a biopreparation A1 with the addition of γ-PGA. The research used biopreparation A1 made of the following strains: Dietzia sp. IN133, Gordonia sp. IN138 Mycolicibacterium frederiksbergense IN53, Rhodococcus erythropolis IN119, Rhodococcus sp. IN136 and Pseudomonas sp. IN132. The experiments were carried out in laboratory conditions (microbiological tests, respirometric tests, and in semi-technical conditions (ex-situ prism method). The biodegradation efficiency was assessed on the basis of respirometric tests, chromatographic analyses and toxicological tests. As a result of inoculation of AB soil with the biopreparation A1 within 6 months, a reduction of total petroleum hydrocarbons (TPH) (66.03%), BTEX (80.08%) and PAHs (38.86%) was achieved and its toxicity was reduced. Inoculation of AB soil with the biopreparation A1 with the addition of γ-PGA reduced the concentration of TPH, BTEX and PAHs by 79.21%, 90.19%, and 51.18%, respectively, and reduced its toxicity. The conducted research has shown that the addition of γ-PGA affects the efficiency of the biodegradation process of petroleum pollutants, increasing the degree of TPH biodegradation by 13.18%, BTEX by 10.11% and PAHs by 12.32% compared to pure biopreparation A1.

Selective biodegradation of dibenzothiophene and alkyl dibenzothiophenes in crude oils from the Linpan oilfield, Bohai Bay basin, eastern China

The biodegradation of dibenzothiophene (DBT) and alkyl dibenzothiophenes (DBTs) were studied in crude oils from the Linpan oilfield, Bohai Bay basin, eastern China. The crude oils selected from the oilfield had been subjected to different degrees of biodegradation, i.e., non-biodegraded to severely biodegraded. With increasing biodegradation extent, the concentration of total DBTs in the crude oils rises from non- to heavily-biodegraded degrees, and then declines from heavily to severely-biodegraded degrees meanwhile the paraffins in the crude oils have been thoroughly removed. The differences in biodegradation rates had been observed between the homologues of alkyl DBTs, and the susceptibility to biodegradation of these homologues declines with increasing of the alkyl substituent number. Selective biodegradation occurred due to differences of carbon positions of alkyl substituents on molecular structure of DBTs. The sulfur-shielded isomers, such as 4,6-dimethyldibenzothiophene and 4-ethyl-6-methyldibenzothiophene, were more susceptible to biodegradation than the sulfur-exposed isomers, for example 2,8-dimethyldibenzothiophene and 1,2,7-+1,2,8-trimethyldibenzothiophenes (co-eluted as one peak in mass chromatograms). However, selective biodegradation of C4-DBTs isomers was less remarkable than the isomers of C2- and C3-DBTs, which reflected the complex processes of biodegradation.

Backbone degradable poly(acrylic acid) analogue via radical ring-opening copolymerization and enhanced biodegradability

Degradable poly(acrylic acid) has been prepared via free radical ring-opening copolymerization of tert-butyl acrylate and 2-methylene-1,3-dioxepane followed by tert-butyl deprotection, under acidic conditions. The resulting degradable poly(acrylic acid) analogue possesses ester groups within the backbone, which facilitate environmental hydrolysis into short chain oligomers, which subsequently undergo biodegradation. The degradable poly(acrylic acid) reported displays a significant degree of biodegradability (27.50% in 28 days) under environmental conditions, when compared to a conventional all carbon backbone non-degradable version, which shows no biodegradability.

BIOMATERIALS BASED ON COLLAGEN AND POLYSACCHARIDES INVOLVED IN TISSUE REGENERATION - MINIREVIEW

This article aims to review the specialized literature regarding biomaterials based on collagen and polysaccharides useful in tissue regeneration. Collagen is the predominant protein in the animal body. The rather large spread of this protein, its physico-chemical and biological properties allow its use in the creation of materials that can come into direct contact with animal tissues, including human ones. Biomaterials based on collagen play an important role in tissue engineering. These can be spongy matrices, membranes or hydrogels. Combining collagen with different polysaccharides (cellulose, chitosan, alginate, hyaluronic acid) leads to the improvement of the physical-chemical, mechanical and biological properties of the resulting biomaterials. Studies have shown that they can be used in the regeneration of epidermal tissue, bone tissue, neural tissue, eye tissues. Collagen combined with chitosan can be used in bioprinting. The studies carried out on cell cultures demonstrated that the biomaterials resulting from the combination of collagen with different polysaccharides have a low degree of cytotoxicity. In various articles it was shown that these biomaterials have the physico-chemical properties (degree of biodegradability, degree of swelling, degree of porosity) necessary for tissue regenerative engineering.

The use of biological markers in organic geochemical investigations of the origin and geological history of crude oils (I) and in the assessment of oil pollution of rivers and river sediments of Serbia (II)

Biological markers (BMs) are organic compounds in oils in which a precursor is known, and during the transformation of organic matter these compounds undergo certain structural and stereochemical changes. Based on the established precursors of BMs, the origin of the examined oils can be estimated, and based on the intensity and the type of changes and also geological history. It includes defining the deposition medium, the degree of maturation, the length of the oil migration path, the degree of biodegradation. The most studied and applied BMs are normal alkanes, isoprenoid aliphatic alkanes pristane and phytane, and polycyclic alkanes of the sterane and terapane type. On the other hand, in the environmental chemistry, these compounds can significantly contribute to the identification of petroleum pollutants, as well as to the assessment of the migration mechanism and the intensity of biodegradation. This review paper first presents the results related to the application of BMs in the organic geochemical correlations of oil in the south-eastern part of the Pannonian Basin (I). The second part provides an overview of those researches in which the same BMs were used in the identification of oil pollutants and in monitoring their changes during the migration and the biodegradation in rivers and river sediments of Serbia (II).

Biodegradable low-density polyethylene with natural rubber additives as a promising "eco-friendly" packaging material

Currently, there is a rapid growth in the consumption of polymeric materials. The authors evaluate polymeric materials based on a synthetic polymer - polyethylene - as the most produced and natural polymers, such as natural rubber. This work is devoted to the creation of biodegradable polymeric materials based on low density polyethylene and natural rubber. The main factors influencing the value of the degree of biodegradability of composites are considered. The physical and mechanical properties of the compositions are considered.

Effects of Marine Sand on the Microbial Degradation of Biodegradable Plastics in Seawater and Biofilm Communities that Formed on Plastic Surfaces.

Four types of biodegradable plastics were evaluated for their biodegradability in seawater collected at Ajigaura coast, Japan, in the presence or absence of marine sand. One of the plastics, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), showed a degree of biodegradation in a seawater sample, and the addition of marine sand markedly accelerated its biodegradation. The addition of marine sand did not affect the bacterial composition of the biofilm that formed on PHBH, and the family Rhodobacteraceae, which was predicted to contribute to the degradation of PHBH, was dominant in biofilm communities regardless of the addition of marine sand. Marine sand may serve as a bacterial source, resulting in the accelerated degradation of PHBH.

Evaluation of toxicity and biodegradation of thermoplastic starch foams with modified starch

Packaging made with thermoplastic starch (TPS) foams is a great alternative to replace non-biodegradable single-use packaging. TPS foams are of great interest, as they are biodegradable and from renewable sources. Although these foams are hydrophilic, chemical modifications to the starch used to make the foams can make them more resistant to the action of water and moisture. These modifications make the starch more hydrophobic, but they can affect the biotoxicity and biodegradation properties of these starches, important characteristics for environmentally friendly materials. In this work, the toxicity and biodegradability of TPS foams with modified starches were studied. Four types of starch were tested: acetylated starch, esterified starch, 3-chloropropyl trimethoxysilane starch and methyltrimethoxysilane starch. To evaluate the samples, the Allium cepa test, composting, biodegradation via respirometry and enzymatic degradation were used. The results showed that acetylated starch and esterified starch showed toxicity and that all foams showed some degree of biodegradability.

Comparative Analysis of Collagen-Containing Waste Biodegradation, Amino Acid, Peptide and Carbohydrate Composition of Hydrolysis Products

This paper aimed to study the biodegradation of collagen-containing waste (pork skin) induced by collagenase and Neutrase 1.5 MG enzymes and compare the amino acid, peptide, and carbohydrate composition of hydrolysis products. It was found that the degree of biodegradation of collagen-containing raw materials (pork skin) reached 78% when using an enzyme preparation (collagenase with a concentration of 250 U/g of the substrate) at pH 7.0, 40 °C, and a 360 min process duration. It was shown that the content of peptides with a molecular weight of 6.5–14.0 kDa in the hydrolysis products (collagenase) of collagen-containing wastes was 13.4 ± 0.40%, while in the products of hydrolysis (Neutrase 1.5 MG) it was 12.8 ± 0.38%. The study found that the hydrolysis products (Neutrase 1.5 MG) of collagen-containing raw materials contain fewer hexoses, free hexosamines, and hyaluronic acid than the hydrolysis products (collagenase) of collagen-containing raw materials. The content of chondroitin sulfates is practically the same in all samples of hydrolysis products. Proteases with collagenolytic activity are widely used in industry. Recently, they have increasingly been used in pharmaceutical, food, and other industries. Collagenases are promising enzymes for the production of chondroprotectors used for the treatment of osteoarthritis.

Isotopic evidence for the formation of 25-norhopanes via in situ biodegradation in the Permian Lucaogou shales, southern Junggar Basin

Extracts of a set of the Permian Lucaogou shales collected from the southern Junggar Basin in NW China were examined for their molecular compositions and compound-specific isotopic signatures. The distribution of n-alkanes, isoprenoids, steranes, hopanes (C27 to C34) and appearance of 25-norhopanes (C26 to C33) were found to vary between samples, indicating that different degrees of biodegradation occurred in the shale strata. The non-biodegraded sample showed a complete composition of n-alkanes and isoprenoids including pristane (Pr) and phytane (Ph). Moderately biodegraded shales were characterized by near-absence of n-alkanes, but Pr and Ph still showed noticeable contents; 25-norhopanes were not detected. Heavily biodegraded shale had imperceptible content of n-alkanes, isoprenoids and steranes, but a series of abundant 25-norhopanes appeared. Compound-specific isotopic data show negative δ13C values (−44.4‰ to −55.6‰) for the regular hopanes having the same carbon number in all the examined shales, indicating a substantial contribution of methanotrophs to the sediments. Moreover, the 25-norhopanes had consistent δ13C values to the corresponding regular hopanes, which are proposed to be their parent molecules. The distributional and isotopic signatures indicate the 25-norhopanes in the heavily biodegraded Permian Lucaogou shales were genetically formed during in situ biodegradation of the extractable bitumen when the strata were uplifted from depth and may have been linked to the incursion of meteoric water.