Microbial Enzyme Production Research Articles

Plant-plant competition influences temporal dynamism of soil microbial enzyme activity

Root-derived compounds can change rates of soil organic matter decomposition (rhizosphere priming effects) through microbial production of extracellular enzymes. Such soil priming can be affected by plant identity and soil nutrient status. However, the effect of plant-plant competition on the temporal dynamics of soil organic matter turnover processes is not well understood. This study used zymography to detect the spatial and temporal pattern of cellulase and leucine aminopeptidase activity, two enzyme classes involved in soil organic matter turnover. The effect of plant-plant competition on enzyme activity was examined using barley (Hordeum vulgare) plants grown in i) isolation, ii) intra- and iii) inter-cultivar competition. The enzyme activities of leucine aminopeptidase and cellulase were measured from portions of the root system at 18, 25 and 33 days after planting, both along the root axis and in the root associated area with detectable enzyme activity. The activities of cellulase and leucine aminopeptidase were both strongly associated with plant roots, and increased over time. An increase in the area of cellulase activity around roots was delayed when plants were in competition compared to in isolation. A similar response was found for leucine aminopeptidase activity, but only when in intra-cultivar competition, and not when in inter-cultivar competition. Therefore, plant-plant competition had a differential effect on enzyme classes, which was potentially mediated through root exudate composition. This study demonstrates the influence of plant-plant competition on soil microbial activity and provides a potential mechanism by which temporal dynamism in plant resource capture can be mediated.

Hydrolytic enzyme production of endophytic fungi isolated from soybean (Glycine max)

This current approach aimed to isolate endophytic fungi from soybean (Glycine max L.) and to assess for their ability to produce hydrolytic extracellular enzymes such as carboxymethyl cellulase (CMC-ase), xylanase and amylase in order to evaluate their ecological role within the host plant. Ten endophytic fungi were isolated from soybean (roots, stems, and leaves). All isolated endophytes (100%) exhibited CMC-ase, xylanase and amylase activities using the minimal synthetic medium (MSM) for enzyme production supplemented with 2% agar in presence of the appropriate carbon source including carboxymethyl cellulose (CMC) for CMC-ase, xylan for xylanase and starch for amylase). The endophytic isolates showed growth stimulation on CMC and xylan media and were hyperactive in the presence of these substrates more than glucose. On the other hand, starch was investigated as the lower preferable substrate for these endophytes. These relevant results endeavored to explore endophytic fungi and to investigate their production of industrial microbial enzymes.

Studies of the Nutritional, Environmental Effects and Repressive Nature of Simple Sugars on the Production of endo-β-mannanase by Aspergillus flavus PT7 on Solid State Fermentation

Aims: The importance of nutritional and environmental factors in the production of microbial enzymes cannot be overemphasized. Hence, endo-β-mannanase production was systematically studied in a step-wise approach of building up on the experimentally observed conditions favouring the production of this enzyme in Aspergillus flavus PT7.
 Place and Duration of Study: Department of Microbiology, University of Ibadan, Nigeria, between January 2018 and December 2018.
 Methodology: Thirty-eight (38) fungal isolates obtained were screened for mannolytic ability using standard method. The highest producer of endo-β-mannasase was subjected to various production conditions by adjusting the nutritional and environmental factors in view of optimizing the production of this enzyme in the isolate Aspergillus flavus PT7.
 Results: Copra meal was the highest inducer of mannanase production in the isolate at enzyme activity of 85.86±3.93 U/gds. Production increased to 94.54±0.42 when all forms of extraneous nitrogen sources were excluded from the production medium. pH 5.0, temperature 30°C, moisture content at 100% v/w and inoculum size of 8.0% v/w led to the increase in production by 44% (enzyme activity of 153.24±5.69 U/gds) in 5 days of incubation. Allowing the production set up additional two (2) days led to production increase with a recorded enzyme activity of 170.34±4.35 U/gds. Production of endo-β-mannanase in A. flavus PT7 was observed to be inductive as the presence of simple sugars like glucose, galactose, arabinose and xylose led to extended lag period in the production of the enzymes by the isolate.
 Conclusion: Production of endo-β-mannanase by Aspergillus flavus PT7 was successfully optimized in a step-wise and systematic experimental study of the nutritional and environmental growth conditions of the isolate.

Potential of sugar beet vinasse as a feedstock for biocatalyst production within an integrated biorefinery context

AbstractBACKGROUNDThis work explores the feasibility of vinasse as an inexpensive feedstock for industrial biocatalyst production within the context of an integrated sugar beet biorefinery. As an exemplar, production of CV2025 ω‐Transaminase (ω‐TAm) in Escherichia coli BL21 was studied.RESULTSCharacterisation of vinasse showed that it comprised mainly of glycerol along with several reducing sugars, sugar alcohols, acetate, polyphenols and protein. Preliminary results showed E. coli BL21 cell growth and CV2025 ω‐TAm production were feasible in cultures using 17% to 25% (v/v) vinasse with higher concentrations demonstrating inhibitory effects. The d‐galactose present in vinasse facilitated auto‐induction of the pQR801 plasmid enabling CV2025 ω‐TAm expression without addition of expensive Isopropyl‐β‐d‐thiogalactopyranoside (IPTG). Assessment of different vinasse pre‐processing options confirmed simple dilution of the vinasse was sufficient to reduce the concentration of polyphenols to below inhibitory levels. Optimisation experiments, carried out using a controlled, 24‐well microbioreactor platform, showed supplementation of diluted vinasse medium with 10 g L−1 yeast extract enabled enhancements of 2.8, 2.5, 5.4 and 3‐fold in specific growth rate, maximum biomass concentration, CV2025 ω‐TAm volumetric and specific activity, respectively. Investigation into the metabolic preferences of E. coli BL21 when grown in vinasse showed a preference for D‐mannitol utilisation before simultaneous metabolism of glycerol, d‐xylitol, d‐dulcitol and acetate. Scale‐up of optimised conditions for batch CV2025 ω‐TAm production to a 7.5 L stirred tank reactor (STR) was demonstrated based on matched volumetric mass transfer coefficient (kLa). The results showed good comparability with respect to cell growth, substrate consumption and CV2025 ω‐TAm production representing over a 700‐fold volumetric scale translation. Further enhancements in CV2025 ω‐TAm production were possible in the STR when operated at higher kLa values.CONCLUSIONThis work describes the promising application of vinasse for production of microbial enzymes and insights into carbon source utilisation in complex feedstocks. Exploitation of vinasse as a fermentation feedstock could be further extended to other processes involving different microorganisms and target enzymes. © 2018 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

P and N deficiency change the relative abundance and function of rhizosphere microorganisms during cluster root development of white lupin (Lupinus albus L.)

ABSTRACTWe studied microbe-plant interactions of white lupin, a cluster root-forming plant, under low P and N conditions to examine increased nutrient acquisition by plants either by a shift to a more specialized microbial community or changes in microbial enzyme production. White lupin plants were grown in rhizoboxes filled with either P- or N-deficient soil; fertilized soil was used as control. After cultivation of plants in a glasshouse for 41 d, plant growth (shoot and roots) and P and N accumulation in shoots were measured. Microbial functions were analyzed by P- and N-cycling enzymes. The microbial community structure was estimated by fingerprinting (denaturing gradient gel electrophoresis) and sequencing techniques. P deficiency induced the released citrate and acid phosphomonoesterases from cluster roots and stimulated the production of microbe-derived alkaline phosphomonoesterase in the rhizosphere. P deficiency decreased microbial diversity in the cluster root rhizosphere. Increased relative abundance of Burkholderiales in the rhizosphere of P deficient plants might be responsible for the degradation of different organic P fractions such as phytates. N deficiency induced an increase of the number of nodules and P concentration in shoot as well as roots of white lupin. We clarified that high release of citrate from cluster roots might be the preferred mechanisms to meet the P demand of nodulated plants under N deficiency. In addition, the high abundance of Rhizobiales and Rhodospirillales in the rhizosphere of cluster roots showed that the importance of N-fixing microorganisms under N deficiency. The contribution of rhizosphere microorganisms due to similar activities of N-cycling enzymes under the two different N treatments is less important for N nutrition of plants. Further understanding of the regulation of cluster roots under N-deficiency will provide new information on the interactions between P and N nutrition.

Isolation, Production and Application of Bacterial Pectinase for Industrial Use

Production of microbial enzymes at the industrial scale and their commercialization has gained a lot of focus and importance. Some of the industrially important enzymes from microbial origin include lipases, amylases, proteases, xylynases, pectinases etc. The objective of the study was production and application of bacterial pectinase for industrial use (clarification of fruit juices). Here the isolation of microorganism and characterization was done, then pectinase assay was performed and finally fruit juice was clarified using this enzyme. Here decayed orange peel was used as the sample and it was collected from a local market, South Kalamsseri- Cochin. The collected decayed orange part was subjected to serial dilution in order to isolate the organism. The dilutions were then plated on appropriate media (pecin agar media) and spread plate was performed. After the incubation time, colonies with zone were obtained which showed the production of pectinase enzyme. These isolated colonies were then inoculated to the petri plate containing pectin agar media and streak plate was performed. After 24 h incubation, the isolated colonies were subjected to Gram’s staining. It was Gram negative bacilli. The biochemical characterization (IMViC test) was done and VP Citrate tests were positive. Then the colonies were inoculated in Pectinase Production Broth. After 24 h incubation, the media was centrifuged for the isolation of enzymes. The enzyme assay was done by titration technique and the enzyme activity was found to be 0.78 U. This isolated enzyme was used for the clarification of apple juice and lime juice. According to the findings obtained from the study, the clarification of fruit juice by the use of bacterial pectinase is most cost effective and yield good results for industrial use.

Biodegradability of polyethylene by bacteria and fungi from Dandora dumpsite Nairobi-Kenya.

This study aimed at isolating and identifying bacteria and fungi with the capacity to degrade low density polyethylene (LDPE). The level of biodegradation of LDPE sheets with bacterial and fungal inoculums from different sampling points of Dandora dumpsite was evaluated under laboratory conditions. Incubation of the LDPE sheets was done for sixteen weeks at 37°C and 28°C for bacteria and fungi respectively in a shaker incubator. Isolation of effective candidates for biodegradation was done based on the recorded biodegradation outcomes. The extent of biodegradation on the polyethylene sheets was assessed by various techniques including weight loss analysis, Fourier Transform Infrared Spectroscopy (FTIR) and GC-MS. Fourier Transform Infra-Red spectroscopy (FTIR) analysis revealed the appearance of new functional groups attributed to hydrocarbon degradation after incubation with the bacteria and fungi. Analysis of the 16S rDNA and 18S rDNA sequences for bacteria and fungi respectively showed that bacteria belonging to genera Pseudomonas, Bacillus, Brevibacillus, Cellulosimicrobium, Lysinibacillus and fungi of genus Aspergillus were implicated as polyethylene degraders. An overall analysis confirmed that fungi are generally better degraders of polyethylene than bacteria. The highest fungal degradation activity was a mean weight reduction of 36.4±5.53% attributed to Aspergillus oryzae strain A5, 1 (MG779508). The highest degradation activity for bacteria was a mean of 35.72± 4.01% and 20.28± 2.30% attributed to Bacillus cereus strain A5,a (MG645264) and Brevibacillus borstelensis strain B2,2 (MG645267) respectively. Genus Aspergillus, Bacillus and Brevibacillus were confirmed to be good candidates for Low Density Poly Ethene bio-degradation. This was further confirmed by the appearance of the aldehyde, ether and carboxyl functional groups after FTIR analysis of the polythene sheets and the appearance of a ketone which is also an intermediary product in the culture media. To improve this degrading capacity through assessment of optimum conditions for microbial activity and enzyme production will enable these findings to be applied commercially and on a larger scale.

Catalytic power of enzymes decreases with temperature: New insights for understanding soil C cycling and microbial ecology under warming.

Most current models of soil C dynamics predict that climate warming will accelerate soil C mineralization, resulting in a long-term CO2 release and positive feedback to global warming. However, ecosystem warming experiments show that CO2 loss from warmed soils declines to control levels within a few years. Here, we explore the temperature dependence of enzymatic conversion of polymerized soil organic C (SOC) into assimilable compounds, which is presumed the rate-limiting step of SOC mineralization. Combining literature review, modelling and enzyme assays, we studied the effect of temperature on activity of enzymes considering their thermal inactivation and catalytic activity. We defined the catalytic power of enzymes (Epower ) as the cumulative amount of degraded substrate by one unit of enzyme until its complete inactivation. We show a universal pattern of enzyme's thermodynamic properties: activation energy of catalytic activity (EAcat )<activation energy of thermal inactivation (EAinact ). By investing in stable enzymes (high EAinact ) having high catalytic activity (low EAcat ), microorganisms may maximize the Epower of their enzymes. The counterpart of such EAs' hierarchical pattern is the higher relative temperature sensitivity of enzyme inactivation than catalysis, resulting in a reduction in Epower under warming. Our findings could explain the decrease with temperature in soil enzyme pools, microbial biomass (MB) and carbon use efficiency (CUE) reported in some warming experiments and studies monitoring the seasonal variation in soil enzymes. They also suggest that a decrease in soil enzyme pools due to their faster inactivation under warming contributes to the observed attenuation of warming effect on soil C mineralization. This testable theory predicts that the ultimate response of SOC degradation to warming can be positive or negative depending on the relative temperature response of Epower and microbial production of enzymes.

Biotechnological valorization of pineapple stem for pectinase production by Bacillus subtilis BKDS1: Media formulation and statistical optimization for submerged fermentation

Abstract Agro-residues are mainly comprised of complex polysaccharides that might serve as nutrients for microbial growth and production of enzymes. India is one of the largest producers of pineapple and along with the expanding pineapple production, associated agro-wastes are also increasing proportionally. In this background, the present study has been endeavored to accomplish valorization of pineapple stem for the economical production of the enzyme, pectinase by Bacillus subtilis BKDS1 using pineapple stem extract (PSE) medium. The results revealed that, the effective concentration of the extract towards producing maximum pectinase enzyme was found to be 12.5% in distilled water. Enhancement of pectinase production in terms of media optimization has been attempted using Plackett-Burman design (PBD) and response surface methodology (RSM). Out of nine variables screened by PBD, only four variables; yeast extract, CaCl2, CaCO3 and inoculum have been selected to affect the pectinase production significantly. The single and interactive effects of all the selected variables have been analyzed using Central composite design (CCD) of RSM. The data revealed that, optimized medium produces a higher concentration of enzyme than unoptimized medium. Further, the efficiency of modified PSE medium for the production of pectinase by submerged fermentation (Smf) has confirmed in laboratory scale fermenter. It has also been found that, enzyme production is achieved at a faster rate in fermenter compared to shaker flasks. Thus, the study as whole highlights the fact that, pineapple stems can be successfully employed in the production of the industrially important enzyme, pectinase using B. subtilis BKDS1. This will in turn, can deliver a lot towards the proper management of agro-wastes and also ensure a better cleaner environment.

A meta-analysis of soil extracellular enzyme activities in response to global change

The crucial biogeochemical processes such as carbon and nutrient cycling are increasingly altered at the ecosystem scale by global environmental changes. Although soil extracellular enzyme activities (EEAs) play a critical role in biogeochemical processes, the global patterns of soil EEAs in a changing world remain elusive. Here, we synthesized eight EEAs involved in carbon (C), nitrogen (N) and phosphorus (P) acquisition in response to seven global change factors based on 132 peer-reviewed papers. Our results showed that elevated CO2 concentration had no significant effects on soil EEAs. Nitrogen addition stimulated C-acquisition (9.1%) and P-acquisition (9.9%) EEAs, but suppressed oxidase activity (−6.8%). Phosphorus addition decreased P-acquisition EEA (−19.8%), while combined N and P addition increased C-acquisition EEA (30.7%). Moreover, decrease in precipitation dramatically suppressed oxidase activity (−47.2%), increase in precipitation marginally stimulated N-acquisition EEA (16.7%), while warming significantly decreased oxidase activity (−10.9%) and had minor positive effect on hydrolytic enzymes. Overall, our results provide some evidence (with exceptions) for the resource allocation theory of microbial enzyme production, and indicate that EEAs are generally more sensitive to nutrient addition than to atmospheric and climate change. We have shown that global environmental changes can alter EEAs, which have implications for soil carbon storage, nutrient cycling, and plant productivity. Further research is needed to elucidate the underlying mechanisms driving the responses of EEAs to global change and to collect data from particularly non-forest ecosystems (e.g., wetland, tundra and desert) and global-change drivers (other than N addition) that lack of EEA data. Our synthesis of the responses of soil enzyme activities to global-change drivers can be used to develop better representations of microbial processes in ecosystem and earth system models.

Novel optimization strategy for tannase production through a modified solid-state fermentation system

BackgroundHigh amounts of insoluble substrates exist in the traditional solid-state fermentation (SSF) system. The presence of these substrates complicates the determination of microbial biomass. Thus, enzyme activity is used as the sole index for the optimization of the traditional SSF system, and the relationship between microbial growth and enzyme synthesis is always ignored. This study was conducted to address this deficiency. All soluble nutrients from tea stalk were extracted using water. The aqueous extract was then mixed with polyurethane sponge to establish a modified SSF system, which was then used to conduct tannase production. With this system, biomass, enzyme activity, and enzyme productivity could be measured rationally and accurately. Thus, the association between biomass and enzyme activity could be easily identified, and the shortcomings of traditional SSF could be addressed.ResultsDifferent carbon and nitrogen sources exerted different effects on microbial growth and enzyme production. Single-factor experiments showed that glucose and yeast extract greatly improved microbial biomass accumulation and that tannin and (NH4)2SO4 efficiently promoted enzyme productivity. Then, these four factors were optimized through response surface methodology. Tannase activity reached 19.22 U/gds when the added amounts of tannin, glucose, (NH4)2SO4, and yeast extract were 7.49, 8.11, 9.26, and 2.25%, respectively. Tannase activity under the optimized process conditions was 6.36 times higher than that under the initial process conditions. The optimized parameters were directly applied to the traditional tea stalk SSF system. Tannase activity reached 245 U/gds, which is 2.9 times higher than our previously reported value.ConclusionsIn this study, a modified SSF system was established to address the shortcomings of the traditional SSF system. Analysis revealed that enzymatic activity and microbial biomass are closely related, and different carbon and nitrogen sources have different effects on microbial growth and enzyme production. The maximal tannase activity was obtained under the optimal combination of nutrient sources that enhances cell growth and tannase accumulation. Moreover, tannase production through the traditional tea stalk SSF was markedly improved when the optimized parameters were applied. This work provides an innovative approach to bioproduction research through SSF.

Use of Olive Mill Wastewater as a Growth Medium for Superoxide Dismutase and Catalase Production

Microbial processing of food industrial waste, olive mill wastewater (OMW), is a promising route from not only a bioremediation point of view but also for bio‐refinery concept. Enzymes are among numerous products to be valorised from OMW. In this study, production of microbial antioxidant enzymes in OMW is successfully demonstrated for the first time. Superoxide dismutase (SOD) and catalase (CAT) activities by Rhodotorula glutinis cultivated in OMW in parallel with the biodegradation of wastewater are investigated. The effects of different carbon and nitrogen supplements as well as metal ions added to cultivation medium, temperature, and stress agents are examined to increase SOD and CAT activities. The results show that R. glutinis can grow and produce SOD and CAT in OMW medium. Ethanol as a carbon supplement and urea as a nitrogen supplement provide high enzyme activities. Low temperature stimulates SOD and CAT activities. Mg2+ is the most effective metal ion for both enzyme activities. Treatment of cells with H2O2 increases SOD and CAT activities whereas UV light did not affect the activities considerably. At all conditions, more than 75% decrease in total phenol concentration and about 75% consumption of reducing sugar presented in cultivation medium are obtained.

Enzymes of industrial purpose - review of the market of enzyme preparations and prospects for its development

Microbial enzyme preparations are increasingly replacing conventional chemical catalysts in a number of industrial processes. Such drugs, in addition to environmental friendliness and high activity, have a number of advantages over enzyme preparations of vegetable and animal origin, namely: the production of microbial enzymes in bioreactors is easily controlled and predictable; excreted microbiological enzymes are more stable than intracellular animals and plant enzymes; the genetic diversity of microorganisms makes it possible to produce enzyme preparations with a wide range of specificity; microbiological enzymes can be synthesized year-round, in contrast to the production of plant enzymes, which is often seasonal. The leaders of the world market of enzymes are proteases and amylases, which account for 25% and 15%, respectively. Over the past five years, the world market for carbohydrases, including mainly amylases, cellulases and xylanases, has been the fastest growing segment of the enzyme market with an aggregate annual growth rate of more than 7.0%. Another major product of the industrial enzyme market, which has a great potential for growth, is lipases. From the point of view of designation, the main part is represented by food and food enzymes. The Russian market continues to be unsaturated - the current supply is not able to meet the needs of the Russian feed and food industry in enzyme preparations. Enzyme preparations of domestic producers are in demand in forage production, while food industrial enterprises prefer imported products. The most significant enterprises in the enzymatic industry in Russia at the moment are Sibbiofarm, AgroSistema, Agroferment. In the light of the Russian policy of increasing food security, the development of the domestic enzyme industry is an extremely topical task.

On-Site Production of Cellulolytic Enzymes by the Sequential Cultivation Method.

The conversion of renewable lignocellulosic biomass into fuels, chemicals, and high-value materials using the biochemical platform has been considered the most sustainable alternative for the implementation of future biorefineries. However, the high cost of the cellulolytic enzymatic cocktails used in the saccharification step significantly affects the economics of industrial large-scale conversion processes. The on-site production of enzymes, integrated to the biorefinery plant, is being considered as a potential strategy that could be used to reduce costs. In such approach, the microbial production of enzymes can be carried out using the same lignocellulosic biomass as feedstock for fungal development and biofuels production. Most of the microbial cultivation processes for the production of industrial enzymes have been developed using the conventional submerged fermentation. Recently, a sequential solid-state followed by submerged fermentation has been described as a potential alternative cultivation method for cellulolytic enzymes production. This chapter presents the detailed procedure of the sequential cultivation method, which could be employed for the on-site production of the cellulolytic enzymes required to convert lignocellulosic biomass into simple sugars.

Gram-scale production of recombinant microbial enzymes in shake flasks.

Heterologous production of recombinant proteins is a cornerstone of microbiological and biochemical research as well as various biotechnological processes. Yields and quality of produced proteins have a tremendous impact on structural and enzymology studies, development of new biopharmaceuticals and establishing new biocatalytic processes. Majority of current protocols for recombinant protein expression in Escherichia coli exploit batch cultures with complex media, often providing low yields of the target protein due to oxygen transfer limitation, rapid depletion of carbon sources and pH changes during the cultivation. Recently introduced EnBase technology enables fed-batch-like cultivations in shake flasks with continuous glucose release from a soluble starch. In this study, we critically compare the yields of fourteen model enzymes in E. coli cultured in a novel semi-defined medium and in a complex medium. Significant improvements of the volumetric yields 2-31 times were observed for all tested enzymes expressed in enzymatic fed-batch-like cultures with no adverse impact on enzyme structure, stability or activity. Exceptional yields, higher than 1 g of protein per liter of culture, were obtained with six enzymes. We conclude that the novel semi-defined medium tested in this study provides a robust improvement of protein yields in shake flasks without investment into costly bioreactors.

Algal biomass: A sustainable, economical and renewable approach for microbial production of pectinolytic enzymes using submerged and solid state fermentation techniques

In the past decade, algal waste has been used as useful natural resource for production of enormous range of products that have wide economical and commercial importance. Pectinases are group of enzymes that have wide commercial applications. Hence, current study was designed to utilize algal biomass for the production of pectinases using submerged (SmF) and solid state fermentation (SSF) techniques. Different algal sources including brown (Dictyopteris polypodioides, Sargassum wightii and Dictyopteris divaricata) and green algae (Ulva lactuca and Codium tomentosum) were used and U. lactuca was found to be the most suitable substrate. Several bacterial and fungal strains were screened and among them Bacillus licheniformis KIBGE-IB4 was selected based on maximum pectinase production. SmF and SSF were studied utilizing U. lactuca as a substrate and results revealed that enzyme production was favoured by SmF (2457 ± 3.31 U mg−1) as compared to SSF (1432 ± 1.46 U mg−1). Parametric optimization of pectinase production indicated that B. licheniformis KIBGE-IB4 requires 10.0 g L–1 U. lactuca as a biomass in the medium with a pH 7.0 when incubated at 37 °C for 24 hours. Likewise, production of pectinase using algal resource was also compared with that of the conventional agricultural biomass and it was observed that when U. lactuca was used, the selected bacterial isolate produced a higher yield of enzyme than sugarcane bagasse and rice husk. Hence, it is anticipated that algal biomass can be efficiently utilized as an environmental friendly bioresource for the production of industrially important hydrolytic enzymes.

Rolling in the deep: Priming effects in earthworm biopores in topsoil and subsoil

Priming effect is the change of soil organic matter (SOM) decomposition due to the addition of labile carbon (C) sources. Earthworms incorporate organic matter into their burrow-linings thereby creating preferred habitats for microorganisms, but the roles of such burrows in priming effect initiation is unknown. Here we study the mechanisms driving SOM decomposition in top- and subsoil biopores and additionally in the rhizosphere. Given the topsoil was newly formed after ploughing 10 months prior to sampling, we hypothesized that (1) SOM accessibility, enzyme activities and efficiency of enzymatic reaction (Ka) are main drivers of different priming effect in biopores vs. bulk soil and rhizosphere, subsoil vs. topsoil and (2) the production of microbial enzymes in biopores depends on microbial community composition. To test these hypotheses, biopores formed by Lumbricus terrestris L. and bulk soil were sampled from topsoil (0–30 cm) and two subsoil depths (45–75 and 75–105 cm). Additionally, rhizosphere samples were taken from the topsoil. Total organic C (Corg), total N (TN), total P (TP) and enzyme activities involved in C-, N-, and P-cycling (cellobiohydrolase, β-glucosidase, xylanase, chitinase, leucine aminopeptidase and phosphatase) were measured. Priming effects were calculated as the difference in SOM-derived CO2 from soil with or without 14C-labeled glucose addition.Enzyme activities (Vmax) and the catalytic efficiency (Ka) were higher in biopores compared to bulk soil and the rhizosphere, indicating that the most active microbial community occurred at this site. Negative correlations between some enzymes and C:N ratio in bulk soil are explained by higher content of fresh organic C in the topsoil, and the corresponding C and nutrient limitations in the subsoil. The positive correlation between enzyme activities and Corg or TN in biopores, however, was associated with the decrease of C and TN with pore age in the subsoil. In the subsoil, priming effect in biopores was 2.5 times higher than bulk soil, resulting from the favorable conditions for microorganisms in biopores and the stimulation of microbial activities by earthworm mucus. We conclude that earthworm burrows provide not only the linkage between top- and subsoil for C and nutrients, but strongly increase microbial activities and accelerate SOM turnover in subsoil, contributing to nutrient mobilization for roots.

Conjugated Linolenic Acid Production by Lactobacilli Isolated from Human Milk, Feces and Fermented Dairy Products

Background: Many investigations have attributed bio-functional properties to a range of conjugated fatty acids (CFAs) of which the conjugated linoleic acid (CLA) and conjugated linolenic acid (CLNA) isomers have displayed potent health beneficial effects in a large number of in vitro and in vivo studies. CLNA isomers are naturally present in high concentrations in a variety of seed oils but relatively in small amount in meat and dairy products. However, some reports have shown the microbial production of such enzymes by lactic acid bacteria that convert linolenic acid (LNA) into CLNA. Present study aims to isolate CLNA producing lactobacilli of different origins and their potential to produce different CLNA isomers in MRS media. Keywords: Lactobacilli, conjugated fatty acid, conjugated linolenic acid, α-linolenic acid and conjugated linoleic acid, linoleate isomerase gene.

Differential Responses of Soil Microbial Community to Four-Decade Long Grazing and Cultivation in a Semi-Arid Grassland

Grazing and cultivation are two important management practices worldwide that can cause significant soil organic carbon (SOC) losses. However, it remains elusive how soil microbes have responded to soil carbon changes under these two practices. Based on a four-decade long field experiment, this study investigated the effects of grazing and cultivation on SOC stocks and microbial properties in the semi-arid grasslands of China. We hypothesize that grazing and cultivation would deplete SOC and depress microbial activities under both practices. However, our hypotheses were only partially supported. As compared with the adjacent indigenous grasslands, SOC and microbial biomass carbon (MBC) were decreased by 20% or more under grazing and cultivation, which is consistent with the reduction of fungi abundance by 40% and 71%, respectively. The abundance of bacteria and actinomycetes was decreased under grazing but increased under cultivation, which likely enhanced microbial diversity in cultivation. Invertase activity decreased under the two treatments, while urease activity increased under grazing. These results suggest that nitrogen fertilizer input during cultivation may preferentially favor bacterial growth, in spite of SOC loss, due to rapid decomposition, while overgrazing may deteriorate the nitrogen supply to belowground microbes, thus stimulating the microbial production of nitrogen acquisition enzymes. This decade-long study demonstrated differential soil microbial responses under grazing and cultivation and has important applications for better management practices in the grassland ecosystem.

Fermentative Production of Microbial Enzymes and their Applications: Present status and future prospects

Fermentative Production of Microbial Enzymes and their Applications: Present status and future prospects