Fungal biodegradation of poly(butylene adipate-co-terephthalate)-polylactic acid-thermoplastic starch based commercial bio-plastic film at ambient conditions.

Microbial biodegradation of commercially available poly(butylene adipate-co-terephthalate)-polylactic acid-thermoplastic starch based bio-plastic has been pursued at high temperatures exceeding 55 °C. Herein, we first reported three newly isolated fungal strains from farmland soil samples of Republic of Korea namely, Pyrenochaetopsis sp. strain K2, Staphylotrichum sp. S2-1, and Humicola sp. strain S2-3 were capable of degrading a commercial bio-plastic film with degradation rates of 9.5, 8.6, and 12.2%, respectively after 3 months incubation at ambient conditions. Scanning electron microscopy (SEM) analyses showed that bio-plastic film was extensively fragmented with severe cracking on the surface structure after incubation with isolated fungal strains. X-ray diffraction (XRD) analysis also revealed that high crystallinity of the commercial bio-plastic film was significantly decreased after degradation by fungal strains. Liquid chromatography-mass spectrometry (LC-MS) analyses of the fungal culture supernatants containing the bio-plastic film showed the peaks for adipic acid, terephthalic acid (TPA), and terephthalate-butylene (TB) as major metabolites, suggesting cleavage of ester bonds and accumulation of TPA. Furthermore, a consortium of fungal strain K2 with TPA degrading bacterium Pigmentiphaga sp. strain P3-2 isolated from the same sampling site exhibited faster degradation rate of the bio-plastic film within 1 month of incubation with achieving complete biodegradation of accumulated TPA. We assume that the extracellular lipase activity presented in the fungal cultures could hydrolyze the ester bonds of PBAT component of bio-plastic film. Taken together, the fungal and bacterial consortium investigated herein could be beneficial for efficient biodegradation of the commercial bio-plastic film at ambient conditions.

Life under the snow: A year-round transcriptome analysis of Antarctic mosses in natural habitats provides insight into the molecular adaptation of plants under extreme environment.

Mosses are vital components of ecosystems, exhibiting remarkable adaptability across diverse habitats from deserts to polar ice caps. Sanionia uncinata (Hedw.) Loeske, a dominant Antarctic moss survives extreme environmental condition through perennial lifecycles involving growth and dormancy alternation. This study explores genetic controls and molecular mechanisms enabling S. uncinata to cope with seasonality of the Antarctic environment. We analysed the seasonal transcriptome dynamics of S. uncinata collected monthly from February 2015 to January 2016 in King George Island, Antarctica. Findings indicate that genes involved in plant growth were predominantly upregulated in Antarctic summer, while those associated with protein synthesis and cell cycle showed marked expression during the winter-to-summer transition. Genes implicated in cellular stress and abscisic acid signalling were highly expressed in winter. Further, validation included a comparison of the Antarctic field transcriptome data with controlled environment simulation of Antarctic summer and winter temperatures, which revealed consistent gene expression patterns in both datasets. This proposes a seasonal gene regulatory model of S. uncinate to understand moss adaptation to extreme environments. Additionally, this data set is a valuable resource for predicting genetic responses to climatic fluctuations, enhancing our knowledge of Antarctic flora's resilience to global climate change.

Microbial metabolic responses and CO2 emissions differentiated by soil water content variation in subarctic tundra soils.

Recent rapid air temperature increases across the northern-latitude tundra have prolonged permafrost thawing and snow melting periods, resulting in increased soil temperature (Ts) and volumetric soil water content (SWC). Under prolonged soil warming at 8°C, Alaskan tundra soils were incubated in a microcosm system and examined for the SWC differential influence on the microbial decomposition activity of large molecular weight (MW) humic substances (HS). When one microcosm soil (AKC1-1) was incubated at a constant SWC of 41% for 90 days (T = 90) and then SWC was gradually decreased from 41% to 29% for another T = 90, the initial HS was partly depolymerized. In contrast, in AKC1-2 incubated at a gradually decreasing SWC from the initial 32% to 10% for T = 90 and then increasing to 27% for another T = 90, HS depolymerization was undetected. Overall, the microbial communities in AKC1-1 could maintain metabolic activity at sufficient and constant SWC during the initial T = 90 incubation. In contrast, AKC1-2 microbes may have been damaged by drought stress during the drying SWC regimen, possibly resulting in the loss of HS decomposition activity, which did not recover even after re-wetting to an optimal SWC range (20-40%). After T = 90, the CO2 production in both treatments was attributed to the increased decomposition of small-MW organic compounds (including aerobic HS-degradative products) within an optimal SWC range. We expect this study to provide new insights into the early effects of warming- and topography-induced SWC variations on the microbial contribution to CO2 emissions via HS decomposition in northern-latitude tundra soil.

Temperature sensitivity of Antarctic soil-humic substance degradation by cold-adapted bacteria.

Heteropolymer humic substances (HS) are the largest constituents of soil organic matter and are key components that affect plant and microbial growth in maritime Antarctic tundra. We investigated HS decomposition in Antarctic tundra soils from distinct sites by incubating samples at 5°C or 8°C (within a natural soil thawing temperature range of -3.8°C to 9.6°C) for 90 days (average Antarctic summer period). This continuous 3-month artificial incubation maintained a higher total soil temperature than that in natural conditions. The long-term warming effects rapidly decreased HS content during the initial incubation, with no significant difference between 5°C and 8°C. In the presence of Antarctic tundra soil heterogeneity, the relative abundance of Proteobacteria (one of the major bacterial phyla in cold soil environments) increased during HS decomposition, which was more significant at 8°C than at 5°C. Contrasting this, the relative abundance of Actinobacteria (another major group) did not exhibit any significant variation. This microcosm study indicates that higher temperatures or prolonged thawing periods affect the relative abundance of cold-adapted bacterial communities, thereby promoting the rate of microbial HS decomposition. The resulting increase in HS-derived small metabolites will possibly accelerate warming-induced changes in the Antarctic tundra ecosystem.

Involvement of laccase-like enzymes in humic substance degradation by diverse polar soil bacteria.

Humic substances (HS) in soil are widely distributed in cold environments and account for a significant fraction of soil's organic carbon. Bacterial strains (n = 281) were isolated at 15 °C using medium containing humic acids (HA), a principal component of HS, from a variety of polar soil samples: 217 from the Antarctic and 64 from the Arctic. We identified 73 potential HA-degrading bacteria based on 16S rRNA sequence similarity, and these sequences were affiliated with phyla Proteobacteria (73.9%), Actinobacteria (20.5%), and Bacteroidetes (5.5%). HA-degrading strains were further classified into the genera Pseudomonas (51 strains), Rhodococcus (10 strains), or others (12 strains). Most strains degraded HA between 10 and 25 °C, but not above 30 °C, indicating cold-adapted degradation. Thirty unique laccase-like multicopper oxidase (LMCO) gene fragments were PCR-amplified from 71% of the 73 HA-degrading bacterial strains, all of which included conserved copper-binding regions (CBR) I and II, both essential for laccase activity. Bacterial LMCO sequences differed from known fungal laccases; for example, a cysteine residue between CBR I and CBR II in fungal laccases was not detected in bacterial LMCOs. This suggests a bacterial biomarker role for LMCO to predict changes in HS-degradation rates in tundra regions as global climate changes. Computer-aided molecular modeling showed these LMCOs contain a highly-conserved copper-dependent active site formed by three histidine residues between CBR I and CBR II. Phylogenetic- and modeling-based methods confirmed the wide occurrence of LMCO genes in HA-degrading polar soil bacteria and linked their putative gene functions with initial HS-degradation processes.

Improvement of moss photosynthesis by humic acids from Antarctic tundra soil.

There have been several published reports regarding the growth promoting effect of humic acids (HA) on vascular plants; however, the effect of HA on bryophytes is still unknown. Due to the ecological importance of mosses, which dominate the Antarctic flora, we assessed the effectiveness of HA as a biostimulant using three moss species: Antarctic Ceratodon purpureus KMA5038, Arctic Bryum sp. KMR5045, and Physcomitrella patens which inhabits temperate regions. Natural HA (KS1-3_HA) were extracted through acidic precipitation of alkaline extracts from Antarctic tundra soil. Spectroscopic structural properties of KS1-3_HA were characterized and determined to possess several functional groups such as hydroxyl (R-OH) and carboxyl (R-COOH), implying they could have a growth-related biological function. For two polar mosses, increasing HA concentrations correlated with increased growth and photosynthesis. The efficiency for temperate moss increased at lower concentrations tested, but rather began to reduce at the highest HA concentration, indicating that effective concentrations of HA vary depending on the moss species and habitat. Based on these results, Antarctic HA may have ecological role in enhancing the growth and photosynthesis of Antarctic mosses. We believe this is the first study to establish a positive physiological effect of HA on mosses and hope it may serve as a basis for studying the role of HA in preserving the terrestrial ecosystem of Antarctica.

Soil water content as a critical factor for stable bacterial community structure and degradative activity in maritime Antarctic soil.

Recent increases in air temperature across the Antarctic Peninsula may prolong the thawing period and directly affect the soil temperature (Ts) and volumetric soil water content (SWC) in maritime tundra. Under an 8°C soil warming scenario, two customized microcosm systems with maritime Antarctic soils were incubated to investigate the differential influence of SWC on the bacterial community and degradation activity of humic substances (HS), the largest constituent of soil organic carbon and a key component of the terrestrial ecosystem. When the microcosm soil (KS1-4Feb) was incubated for 90 days (T = 90) at a constant SWC of ~32%, the initial HS content (167.0 mg/g of dried soil) decreased to 156.0 mg (approximately 6.6% loss, p < 0.05). However, when another microcosm soil (KS1-4Apr) was incubated with SWCs that gradually decreased from 37% to 9% for T = 90, HS degradation was undetected. The low HS degradative activity persisted, even after the SWC was restored to 30% with water supply for an additional T = 30. Overall bacterial community structure remained relatively stable at a constant SWC setting (KS1-4Feb). In contrast, we saw marked shifts in the bacterial community structure with the changing SWC regimen (KS1-4Apr), suggesting that the soil bacterial communities are vulnerable to drying and re-wetting conditions. These microcosm experiments provide new information regarding the effects of constant SWC and higher Ts on bacterial communities for HS degradation in maritime Antarctic tundra soil.

Antarctic tundra soil metagenome as useful natural resources of cold-active lignocelluolytic enzymes.

Lignocellulose composed of complex carbohydrates and aromatic heteropolymers is one of the principal materials for the production of renewable biofuels. Lignocellulose-degrading genes from cold-adapted bacteria have a potential to increase the productivity of biological treatment of lignocellulose biomass by providing a broad range of treatment temperatures. Antarctic soil metagenomes allow to access novel genes encoding for the cold-active lignocellulose-degrading enzymes, for biotechnological and industrial applications. Here, we investigated the metagenome targeting cold-adapted microbes in Antarctic organic matter-rich soil (KS 2-1) to mine lignolytic and celluloytic enzymes by performing single molecule, real-time metagenomic (SMRT) sequencing. In the assembled Antarctic metagenomic contigs with relative long reads, we found that 162 (1.42%) of total 11,436 genes were annotated as carbohydrate-active enzymes (CAZy). Actinobacteria, the dominant phylum in this soil's metagenome, possessed most of candidates of lignocellulose catabolic genes like glycoside hydrolase families (GH13, GH26, and GH5) and auxiliary activity families (AA7 and AA3). The predicted lignocellulose degradation pathways in Antarctic soil metagenome showed synergistic role of various CAZyme harboring bacterial genera including Streptomyces, Streptosporangium, and Amycolatopsis. From phylogenetic relationships with cellular and environmental enzymes, several genes having potential for participating in overall lignocellulose degradation were also found. The results indicated the presence of lignocellulose-degrading bacteria in Antarctic tundra soil and the potential benefits of the lignocelluolytic enzymes as candidates for cold-active enzymes which will be used for the future biofuel-production industry.

Flavobacterium petrolei sp. nov., a novel psychrophilic, diesel-degrading bacterium isolated from oil-contaminated Arctic soil.

This study presents taxonomic description of two novel diesel-degrading, psychrophilic strains: Kopri-42T and Kopri-43, isolated during screening of oil-degrading psychrotrophs from oil-contaminated Arctic soil. A preliminary 16S rRNA gene sequence and phylogenetic tree analysis indicated that these Arctic strains belonged to the genus Flavobacterium, with the nearest relative being Flavobacterium psychrolimnae LMG 22018T (98.9% sequence similarity). The pairwise 16S rRNA gene sequence identity between strains Kopri-42T and Kopri-43 was 99.7%. The DNA-DNA hybridization value between strain Kopri-42T and Kopri-43 was 88.6 ± 2.1% indicating that Kopri-42T and Kopri-43 represents two strains of the same genomospecies. The average nucleotide identity and in silico DNA-DNA hybridization values between strain Kopri-42T and nearest relative F. psychrolimnae LMG 22018T were 92.4% and 47.9%, respectively. These values support the authenticity of the novel species and confirmed the strain Kopri-42T belonged to the genus Flavobacterium as a new member. The morphological, physiological, biochemical and chemotaxonomic data also distinguished strain Kopri-42T from its closest phylogenetic neighbors. Based on the polyphasic data, strains Kopri-42T and Kopri-43 represents a single novel species of the genus Flavobacterium, for which the name Flavobacterium petrolei sp. nov. is proposed. The type strain is Kopri-42T (=KEMB 9005-710T = KACC 19625T = NBRC 113374T).

Flavobacterium dasani sp. nov., a psychrotolerant bacterium isolated from Arctic soil.

A novel yellow-colored, Gram-stain-negative, aerobic, non-motile, catalase- and oxidase-positive, and rod-shaped psychrotolerant bacterium, designated strain PLR-18-3T, was isolated from Arctic soil and was subjected to polyphasic taxonomic study. Cells were able to grow at 0-30 °C, pH 6.0-10.5, and 0-3.0% (w/v) NaCl concentration. Based on the 16S rRNA gene sequence analysis, this Arctic strain belonged to the genus Flavobacterium, with the closest neighbor being Flavobacterium noncentrifugens R-HLS-17T (96.2% sequence similarity). The strain contained MK-6 as a sole respiratory quinone, phosphatidylethanolamine as the major polar lipid, and summed feature 3 (C16:1ω7c and/or C16:1ω6c), iso-C15:0, iso-C15:0 G, iso-C17:0 3-OH, iso-C15:0 3-OH, anteiso-C15:0, and summed feature 9 (iso-C17:1ω9c and/or C16:010-methyl) as the predominant fatty acids. The DNA G + C content was 37.9 mol%. On the basis of polyphasic data, strain PLR-18-3T represents a novel species of the genus Flavobacterium, for which the name Flavobacterium dasani sp. nov. is proposed. The type strain is PLR-18-3T (=KEMB 9005-713T=KACC 19627T=NBRC 113347T).

Biotechnological Potential of Rhodococcus Biodegradative Pathways.

The genus Rhodococcus is a phylogenetically and catabolically diverse group that has been isolated from diverse environments, including polar and alpine regions, for its versatile ability to degrade a wide variety of natural and synthetic organic compounds. Their metabolic capacity and diversity result from their diverse catabolic genes, which are believed to be obtained through frequent recombination events mediated by large catabolic plasmids. Many rhodococci have been used commercially for the biodegradation of environmental pollutants and for the biocatalytic production of high-value chemicals from low-value materials. Recent studies of their physiology, metabolism, and genome have broadened our knowledge regarding the diverse biotechnological applications that exploit their catabolic enzymes and pathways.

Passive warming effect on soil microbial community and humic substance degradation in maritime Antarctic region.

Although the maritime Antarctic has undergone rapid warming, the effects on indigenous soil-inhabiting microorganisms are not well known. Passive warming experiments using open-top chamber (OTC) have been performed on the Fildes Peninsula in the maritime Antarctic since 2008. When the soil temperature was measured at a depth of 2-5 cm during the 2013-2015 summer seasons, the mean temperature inside OTC (OTC-In) increased by approximately 0.8 °C compared with outside OTC (OTC-Out), while soil chemical and physical characteristics did not change. Soils (2015 summer) from OTC-In and OTC-Out were subjected to analysis for change in microbial community and degradation rate of humic substances (HS, the largest pool of recalcitrant organic carbon in soil). Archaeal and bacterial communities in OTC-In were minimally affected by warming compared with those in OTC-Out, with archaeal methanogenic Thermoplasmata slightly increased in abundance. The abundance of heterotrophic fungi Ascomycota was significantly altered in OTC-In. Total bacterial and fungal biomass in OTC-In increased by 20% compared to OTC-Out, indicating that this may be due to increased microbial degradation activity for soil organic matter (SOM) including HS, which would result in the release of more low-molecular-weight growth substrates from SOM. Despite the effects of warming on the microbial community over the 8-years-experiments warming did not induce any detectable change in content or structure of polymeric HS. These results suggest that increased temperature may have significant and direct effects on soil microbial communities inhabiting maritime Antarctic and that soil microbes would subsequently provide more available carbon sources for other indigenous microbes.

Crystal structure of a cold-active protease (Pro21717) from the psychrophilic bacterium, Pseudoalteromonas arctica PAMC 21717, at 1.4 Å resolution: Structural adaptations to cold and functional analysis of a laundry detergent enzyme.

Enzymes isolated from organisms found in cold habitats generally exhibit higher catalytic activity at low temperatures than their mesophilic homologs and are therefore known as cold-active enzymes. Cold-active proteases are very useful in a variety of biotechnological applications, particularly as active ingredients in laundry and dishwashing detergents, where they provide strong protein-degrading activity in cold water. We identified a cold-active protease (Pro21717) from a psychrophilic bacterium, Pseudoalteromonas arctica PAMC 21717, and determined the crystal structure of its catalytic domain (CD) at a resolution of 1.4 Å. The Pro21717-CD structure shows a conserved subtilisin-like fold with a typical catalytic triad (Asp185, His244, and Ser425) and contains four calcium ions and three disulfide bonds. Interestingly, we observed an unexpected electron density at the substrate-binding site from a co-purified peptide. Although the sequence of this peptide is unknown, analysis of the peptide-complexed structure nonetheless provides some indication of the substrate recognition and binding mode of Pro21717. Moreover, various parameters, including a wide substrate pocket size, an abundant active-site loop content, and a flexible structure provide potential explanations for the cold-adapted properties of Pro21717. In conclusion, this is first structural characterization of a cold-adapted subtilisin-like protease, and these findings provide a structural and functional basis for industrial applications of Pro21717 as a cold-active laundry or dishwashing detergent enzyme.

Transcriptome analysis of Pseudomonas sp. from subarctic tundra soil: pathway description and gene discovery for humic acids degradation.

Although humic acids (HA) are involved in many biological processes in soils and thus their ecological importance has received much attention, the degradative pathways and corresponding catalytic genes underlying the HA degradation by bacteria remain unclear. To unveil those uncertainties, we analyzed transcriptomes extracted from Pseudomonas sp. PAMC 26793 cells time-dependently induced in the presence of HA in a lab flask. Out of 6288 genes, 299 (microarray) and 585 (RNA-seq) were up-regulated by > 2.0-fold in HA-induced cells, compared with controls. A significant portion (9.7% in microarray and 24.1% in RNA-seq) of these genes are predicted to function in the transport and metabolism of small molecule compounds, which could result from microbial HA degradation. To further identify lignin (a surrogate for HA)-degradative genes, 6288 protein sequences were analyzed against carbohydrate-active enzyme database and a self-curated list of putative lignin degradative genes. Out of 19 genes predicted to function in lignin degradation, several genes encoding laccase, dye-decolorizing peroxidase, vanillate O-demethylase oxygenase and reductase, and biphenyl 2,3-dioxygenase were up-regulated > 2.0-fold in RNA-seq. This induction was further confirmed by qRT-PCR, validating the likely involvement of these genes in the degradation of HA.

Metagenomic SMRT Sequencing-Based Exploration of Novel Lignocellulose-Degrading Capability in Wood Detritus from Torreya nucifera in Bija Forest on Jeju Island.

Lignocellulose, composed mostly of cellulose, hemicellulose, and lignin generated through secondary growth of woody plant, is considered as promising resources for biofuel. In order to use lignocellulose as a biofuel, biodegradation besides high-cost chemical treatments were applied, but knowledge on the decomposition of lignocellulose occurring in a natural environment is insufficient. We analyzed the 16S rRNA gene and metagenome to understand how the lignocellulose is decomposed naturally in decayed Torreya nucifera (L) of Bija forest (Bijarim) in Gotjawal, an ecologically distinct environment. A total of 464,360 reads were obtained from 16S rRNA gene sequencing, representing diverse phyla; Proteobacteria (51%), Bacteroidetes (11%) and Actinobacteria (10%). The metagenome analysis using single molecules real-time sequencing revealed that the assembled contigs determined originated from Proteobacteria (58%) and Actinobacteria (10.3%). Carbohydrate Active enZYmes (CAZy)- and Protein families (Pfam)-based analysis showed that Proteobacteria was involved in degrading whole lignocellulose, and Actinobacteria played a role only in a part of hemicellulose degradation. Combining these results, it suggested that Proteobacteria and Actinobacteria had selective biodegradation potential for different lignocellulose substrates. Thus, it is considered that understanding of the systemic microbial degradation pathways may be a useful strategy for recycle of lignocellulosic biomass, and the microbial enzymes in Bija forest can be useful natural resources in industrial processes.

Influence of Soil Characteristics and Proximity to Antarctic Research Stations on Abundance of Antibiotic Resistance Genes in Soils.

Soil is an important environmental reservoir of antibiotic resistance genes (ARGs), which are increasingly recognized as environmental contaminants. Methods to assess the risks associated with the acquisition or transfer of resistance mechanisms are still underdeveloped. Quantification of background levels of antibiotic resistance genes and what alters those is a first step in understanding our environmental resistome. Toward this goal, 62 samples were collected over 3 years from soils near the 30-year old Gondwana Research Station and for 4 years before and during development of the new Jang Bogo Research Station, both at Terra Nova Bay in Antarctica. These sites reflect limited and more extensive human impact, respectively. A qPCR array with 384 primer sets targeting antibiotic resistance genes and mobile genetic elements (MGEs) was used to detect and quantify these genes. A total of 73 ARGs and MGEs encompassing eight major antibiotic resistance gene categories were detected, but most at very low levels. Antarctic soil appeared to be a common reservoir for seven ARGs since they were present in most samples (42%-88%). If the seven widespread genes were removed, there was a correlation between the relative abundance of MGEs and ARGs, more typical of contaminated sites. There was a relationship between ARG content and distance from both research stations, with a significant effect at the Jang Bogo Station especially when excluding the seven widespread genes; however, the relative abundance of ARGs did not increase over the 4 year period. Silt, clay, total organic carbon, and SiO2 were the top edaphic factors that correlated with ARG abundance. Overall, this study identifies that human activity and certain soil characteristics correlate with antibiotic resistance genes in these oligotrophic Antarctic soils and provides a baseline of ARGs and MGEs for future comparisons.

Characterization of ß-N-acetylglucosaminidase from a marine Pseudoalteromonas sp. for application in N-acetyl-glucosamine production.

The psychrotolerant Pseudoalteromonas issachenkonii PAMC 22718 was isolated for its high exo-acting chitinase activity in the Kara Sea, Arctic. An exo-acting chitinase (W-Chi22718) was homogeneously purified from the culture supernatant of PAMC 22718, the molecular weight of which was estimated to be approximately 112 kDa. Due to its ß-N-acetylglucosaminidase activity, W-Chi22718 was able to produce N-acetyl-D-glucosamine (GlcNAc) monomers from chitin oligosaccharide substrates. W-Chi22718 displayed chitinase activity from 0 to 37°C (optimal temperature of 30°C) and maintained activity from pH 6.0 to 9.0 (optimal pH of 7.6). W-Chi22718 exhibited a relative activity of 13 and 35% of maximal activity at 0 and 10°C, respectively, which is comparable to the activities of previously characterized, cold-adapted bacterial chitinases. W-Chi22718 activity was enhanced by K+, Ca2+, and Fe2+, but completely inhibited by Cu2+ and SDS. We found that W-Chi22718 can produce much more (GlcNAcs) from colloidal chitin, working together with previously characterized cold-active endochitinase W-Chi21702. Genome sequencing revealed that the corresponding gene (chi22718_IV) was 2,856 bp encoding a 951 amino acid protein with a calculated molecular weight of approximately 102 kDa.

Enhanced production of protease by Pseudoalteromonas arctica PAMC 21717 via statistical optimization of mineral components and fed-batch fermentation.

The objective of this study was to statistically optimize the mineral components of the nutritional medium required for enhancing the production of a cold-active extracellular serine-type protease, W-Pro21717, by the Antarctic bacterium Pseudoalteromonas arctica PAMC 21717. Skim milk was identified as the major efficient inducer. Among the 12 components included in the unoptimized medium, skim milk, NaCl, Na2SO4, Fe(C6H5O7) (ferric citrate), and KCl were determined, by the Plackett-Burman and Box-Behnken design, to have a major effect on W-Pro21717 production. Fed-batch fermentation (5 L scale) using the mineral-optimized medium supplemented with concentrated skim milk (critical medium component) resulted in a W-Pro21717 activity of 53.4 U/L, a 15-fold increment in production over that obtained using unoptimized flask culture conditions. These findings could be applied to scale up the production of cold-active protease.

Temporal changes in soil bacterial diversity and humic substances degradation in subarctic tundra soil.

Humic substances (HS), primarily humic acids (HA) and fulvic acids (FA), are the largest constituent of soil organic matter. In microcosm systems with subarctic HS-rich tundra soil (site AK 1-75; approximately 5.6 °C during the thawing period) from Council, Alaska, the HA content significantly decreased to 48% after a 99-day incubation at 5 °C as part of a biologically mediated process. Accordingly, levels of FA, a putative byproduct of HA degradation, consistently increased to 172% during an identical incubation process. Culture-independent microbial community analysis showed that during the microcosm experiments, the relative abundance of phyla Proteobacteria (bacteria) and Euryarchaeota (archaea) largely increased, indicating their involvement in HS degradation. When the indigenous bacteria in AK 1-75 were enriched in an artificial mineral medium spiked with HA, the changes in relative abundance were most conspicuous in Proteobacteria (from 60.2 to 79.0%), specifically Betaproteobacteria-related bacteria. One hundred twenty-two HA-degrading bacterial strains, primarily from the genera Paenibacillus (phylum Firmicutes) and Pseudomonas (class Gammaproteobacteria), were cultivated from AK 1-75 and nearby sites. Through culture-dependent analysis with these bacterial isolates, we observed increasing HS-degradation rates in parallel with rising temperatures in a range of 0 °C to 20 °C, with the most notable increase occurring at 8 °C compared to 6 °C. Our results indicate that, although microbial-mediated HS degradation occurs at temperature as low as 5 °C in tundra ecosystems, increasing soil temperature caused by global climate change could enhance HS degradation rates. Extending the thawing period could also increase degradation activity, thereby directly affecting nearby microbial communities and rhizosphere environments.

Enhancing extracellular lipolytic enzyme production in an arctic bacterium, Psychrobacter sp. ArcL13, by using statistical optimization and fed-batch fermentation.

A strain isolated from seawater samples in the Chuckchi Sea and exhibiting extracellular lipolytic activity was identified using 16S rRNA gene sequence analysis as Psychrobacter sp. ArcL13. The lipolytic enzyme exhibited cold-active properties and high hydrolytic activity toward p-nitrophenyl caprylate (C8), p-nitrophenyl decanoate (C10), and sunflower oil. Statistical optimization of the medium components was performed to enhance the production of cold-active extracellular lipolytic activity. Glucose, yeast extract (YE), and NaCl were selected as the main efficient nutrient sources. Fed-batch fermentation using optimized medium with concentrated YE as the main feeding material showed a maximum lipolytic activity of 10.7 U/mL, which was a 21-fold increase in production over unoptimized flask culture conditions. The information obtained in the present study could prove applicable to the production of cold-active lipase on a large scale.