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Microbiology of green fuels
\"A key priority in today's society is the implementation of a sustainable bio-based economy. For such a goal, the production of renewable bioproducts such as biofuels to replace fossil-derived compounds is crucial. In this context, the utilization of microorganisms for the production of biofuels from renewable resources is advantageous in terms of environmental sustainability and it is expected to play an important role in bioeconomy in the near future. In this sense, green fuel synthesis from agro-industrial organic wastes by microorganisms will boost circular economy. The success of the biotechnological biofuel production process requires, however, conversion microorganism capable of both efficiently assimilating the major derived carbon sources and diverting their metabolites towards the specific fuel. This book aims to show recent advances in the production of green fuels by means of microorganisms. Promising processes and microorganisms involved in the biofuel production will be provided and discussed to give and in-depth overview of the state of the art with broad spectrum of microorganisms and biofuels. For the sustainability of green fuel technologies, the book will also address biosafety of different production technologies and, social and political interest in promoting green fuels. These facts make this book very valuable for biofuels companies and scientific community\"-- Provided by publisher.
Book
global analysis of soil microbial biomass carbon, nitrogen and phosphorus in terrestrial ecosystems
AIM: To estimate the concentrations, stoichiometry and storage of soil microbial biomass carbon (C), nitrogen (N) and phosphorus (P) at biome and global scales. LOCATION: Global. METHOD: We collected 3422 data points to summarize the concentrations and stoichiometry of C, N and P in soils, soil microbial biomass at global and biome levels, and to estimate the global storage of soil microbial biomass C and N. RESULTS: The results show that concentrations of C, N and P in soils and soil microbial biomass vary substantially across biomes; the fractions of soil elements C, N and P in soil microbial biomass are 1.2, 2.6 and 8.0%, respectively. The best estimates of C:N:P stoichiometry for soil elements and soil microbial biomass are 287:17:1 and 42:6:1, respectively, at global scale, and they vary in a wide range among biomes. The vertical distribution of soil microbial biomass follows the distribution of roots up to 1 m depth. MAIN CONCLUSIONS: The global storage of soil microbial biomass C and N were estimated to be 16.7 Pg C and 2.6 Pg N in the 0–30 cm soil profiles, and 23.2 Pg C and 3.7 Pg N in the 0–100 cm soil profiles. We did not estimate P in soil microbial biomass due to insufficient data and insignificant correlation between soil total P and climate variables used for spatial extrapolation. The spatial patterns of soil microbial biomass C and N were consistent with those of soil organic C and total N, i.e. high density in northern high latitude, and low density in low latitudes and the Southern Hemisphere.
Journal Article
Global pattern and controls of soil microbial metabolic quotient
The microbial metabolic quotient (MMQ), microbial respiration per unit of biomass, is a fundamental factor controlling heterotrophic respiration, the largest carbon flux in soils. The magnitude and controls of MMQ at regional scale remain uncertain. We compiled a comprehensive data set of MMQ to investigate the global patterns and controls of MMQ in top 30 cm soils. Published MMQ values, generally measured in laboratory microcosms, were adjusted on ambient soil temperature using long-term (30 yr) average site soil temperature and a Q₁₀ = 2. The area-weighted global average of MMQ_Soil is estimated as 1.8 (1.5–2.2) (95% confidence interval) μmol C·h⁻¹·mmol⁻¹ microbial biomass carbon (MBC) with substantial variations across biomes and between cropland and natural ecosystems. Variation was most closely associated with biological factors, followed by edaphic and meteorological parameters. MMQ_Soil was greatest in sandy clay and sandy clay loam and showed a pH maximum of 6.7 ± 0.1 (mean ± se). At large scale, MMQ_Soil varied with latitude and mean annual temperature (MAT), and was negatively correlated with microbial N:P ratio, supporting growth rate theory. These trends led to large differences in MMQ_Soil between natural ecosystems and cropland. When MMQ was adjusted to 11°C (MMQ_Ref), the global MAT in the top 30 cm of soils, the area-weighted global averages of MMQ_Ref was 1.5 (1.3–1.8) μmol C-mmol MBC⁻¹·h⁻¹. The values, trends, and controls of MMQ_Soil add to our understanding of soil microbial influences on soil carbon cycling and could be used to represent microbial activity in global carbon models.
Journal Article
Global distribution of microbial abundance and biomass in subseafloor sediment
The global geographic distribution of subseafloor sedimentary microbes and the cause(s) of that distribution are largely unexplored. Here, we show that total microbial cell abundance in subseafloor sediment varies between sites by ca. five orders of magnitude. This variation is strongly correlated with mean sedimentation rate and distance from land. Based on these correlations, we estimate global subseafloor sedimentary microbial abundance to be 2.9⋅10 ²⁹ cells [corresponding to 4.1 petagram (Pg) C and ∼0.6% of Earth’s total living biomass]. This estimate of subseafloor sedimentary microbial abundance is roughly equal to previous estimates of total microbial abundance in seawater and total microbial abundance in soil. It is much lower than previous estimates of subseafloor sedimentary microbial abundance. In consequence, we estimate Earth’s total number of microbes and total living biomass to be, respectively, 50–78% and 10–45% lower than previous estimates.
Journal Article
Global drivers and patterns of microbial abundance in soil
Aim: While soil microorganisms play key roles in Earth's biogeochemical cycles, methodological constraints and sparse data have hampered our ability to describe and understand the global distribution of soil microbial biomass. Here, we present a comprehensive quantification of the environmental drivers of soil microbial biomass. Location: Global. Methods: We used a comprehensive global dataset of georeferenced soil microbial biomass estimates and high-resolution climatic and soil data.
Results: We show that microbial biomass carbon (C
Mic
)is primarily driven by moisture availability, with this single variable accounting for 34% of the global variance. For the microbial carbon-to-soil organic carbon ratio (C
Mic
/C
org
) soil nitrogen content was an equally important driver as moisture. In contrast, temperature was not a significant predictor of microbial biomass patterns at a global scale, while temperature likely has an indirect effect on microbial biomass by influencing rates of evapotranspiration and decomposition. As our models explain an unprecedented 50% of the global variance of C
Mic
and C
Mic
/C
Org
, we were able to leverage gridded environmental information to build the first spatially explicit global estimates of microbial biomass and quantified the global soil microbial carbon pool to equal 14.6 Pg C.
Main Conclusions: Our unbiased models allowed us to build the first global spatially explicit predictions of microbial biomass. These patterns show that soil microbial biomass is not primarily driven by temperature, but instead, biomass is more heterogeneous through the effects of moisture availability and soil nutrients. Our global estimates provide important data for integration into large-scale carbon and nutrient models that may imply a major step forward in our ability to predict the global carbon balance, now and in a future climate.
Journal Article
Changes in soil biochemical properties following replacement of Banj oak forest with Chir pine in Central Himalaya, India
IntroductionIn Central Himalaya, anthropogenic activities have led to the widespread replacement of Banj oak (Quercus leucotrichophora) forest by Chir pine (Pinus roxburghii) for decades. This study was conducted to determine how natural Banj oak, Chir pine, and mixed oak-pine forest would differ in soil microbial biomass and soil nutrients. Soil microbial biomass nitrogen (SMBN) and phosphorus (SMBP), soil organic carbon (SOC) total nitrogen (TN), and total phosphorus (TP) in the 0 to 15 cm soil layer were investigated in the Central Himalayan region in the stands of Banj oak, mixed oak-pine, and Chir pine forest.ResultsThe SMBN and SMBP were significantly higher in Banj oak and mixed oak-pine forest as compared to Chir pine forest. The ratios of SMBN to TN (SMBN/TN) and SMBP to TP (SMBP/TP) were significantly higher in the Chir pine forest, indicating that in this forest, the proportion of microbial biomass N and P to total soil N and P was higher as compared to Banj oak forest. A similar pattern of variation was found in relation to season across the forests, all with an apparent peak in the rainy season.ConclusionThese results indicate that low microbial biomass N and P may be one of the reasons to create a nutrient poor site in Chir pine forest. The collection of pine litter by local people also impairs the return of nutrients to the soil and makes it difficult for Banj oak to re-invade areas occupied by Chir pine. This calls for cautions in large-scale conversions of the Banj oak forests to coniferous plantations as a forest management practice on concerns of sustaining soil productivity.
Journal Article
Soil microbial biomass phosphorus can serve as an index to reflect soil phosphorus fertility
The effect and relative contributions of C and P inputs on soil microbial biomass P (MBP) accumulation were studied in three long-term soil fertility experiments with various soil and climate characteristics at Qiyang, Yangling, and Wulumuqi. The maximum of soil MBP in all three sites was 47.8 mg P kg-1. The MBP accumulated per unit in soil (mg P kg-1 soil) was correlated with a 4.91 mg kg-1 increase in Olsen P. For each unit increase in P surplus (kg P ha-1), manure C (kg C ha-1), and stubble C (kg C ha-1), MBP accumulation increased by 330, 3.7, and 13 units (μg P kg-1 soil), respectively. The soil MBP was positively correlated with crop yield and P uptake, making the soil MBP a useful soil P fertility index. The critical levels of the soil MBP pool were 140 kg ha-1, 57–62 kg ha-1, and 33–35 kg ha-1 in acidic red soil, loessial soil, and grey desert soil, respectively. This is the first report to establish a quantitative index of soil fertility based on the soil MBP pool. Our findings demonstrate that C input is a good driver of soil MBP accumulation. Integration of the soil MBP as an index of soil P fertility into agricultural P management is useful to help manage mineral P fertilizers as part of sustainable agricultural practices.
Journal Article
Linking microbial C:N:P stoichiometry to microbial community and abiotic factors along a 3500-km grassland transect on the Tibetan Plateau
Aim: To explore large-scale patterns and the drivers of carbon:nitrogen:phosphorus (C:N:P) stoichiometry in heterotrophic microbes. Location: A 3500-km grassland transect on the Tibetan Plateau. Methods: We investigated large-scale C:N:P stoichiometry patterns in the soil microbial biomass and their relationships with abiotic factors and soil microbial community structures by obtaining soil samples from 173 sites across the Tibetan alpine grasslands. Results: C:N:P ratios in the soil microbial biomass varied widely among grassland types, with higher microbial C:N, C:P and N:P ratios in the alpine steppe than the alpine meadow. The soil microbial C:N:P ratio (81:6:1) in the alpine steppe was significantly wider than the global average (42:6:1). Combined stepwise regression and generalized additive models revealed that variations in the microbial C:N ratio were primarily related to abiotic variables, with the microbial C:N ratio exhibiting a decreasing trend along the precipitation gradient. In contrast, variations in microbial C:P and N:P ratios were primarily associated with shifts in the community structure of soil microbes. The microbial C:P and N:P ratios were both negatively associated with all components of the soil microbial communities. However, the fungi to bacteria ratio only regulated the microbial C:P ratio. Main conclusions: These results demonstrate that microbial C:N:P stoichiometry exhibits significant flexibility across various ecosystem types. This flexibility is partly induced by shifts in microbial community structure and variations in environmental conditions.
Journal Article
Does arbuscular mycorrhizal fungi inoculation influence soil carbon sequestration?
Whether arbuscular mycorrhizal fungi (AMF) inoculation promotes soil C sequestration is largely unknown. Here, meta-analysis and logistic regression were applied to study the ecological effects of AMF inoculation on soil organic C (SOC) turnover and plant growth under different inoculation manipulations, plant traits, and soil conditions. Results showed that AMF inoculation generally increased SOC stock and plant biomass accumulation. Soil sterilization, unsterilized inoculum wash (a filtrate of mycorrhizal inoculum excluding AMF) addition in non-mycorrhizal treatments, experimental type, and inoculated AMF species influenced soil microbial biomass C (MBC) but had no impact on SOC turnover. Plant root system, initial SOC content, and soil pH were the key factors that influenced the AMF-mediated SOC turnover. AMF inoculation in fertile or acidic soils might deplete SOC. The symbiosis between tap-rooted plants and AMF was more likely to sequestrate C into the soil compared to fibrous-rooted plants. Moreover, plant total dry biomass largely relied on its own photosynthetic pathway although AMF was introduced. Collectively, our results suggest that AMF inoculation is a promising approach for soil C sequestration.
Journal Article
Increased microbial carbon use efficiency and turnover rate drive soil organic carbon storage in old-aged forest on the southeastern Tibetan Plateau
It is widely accepted that old-aged forest can accumulate soil organic carbon (SOC). How microbial physiological traits respond to forest age and whether they drive SOC sequestration in old-aged forest remain elusive. Therefore, we compared the microbial C use efficiency (CUE), biomass turnover rate (rB), microbial biomass C (MBC) and necromass C (MNC) across soil profiles from middle and old-aged forest and evaluated how these microbial traits are related to SOC storage. The results revealed that both forests could accumulate SOC and old-aged forest supported higher SOC storage than middle-aged forest from 2005 to 2020. Moreover, SOC was concentrated on the surface soils of middle-aged forest, whereas it was more distributed across the deeper soil profile in old-aged forest. Compared with middle-aged forest, the O, A and B soil layers of old-aged forest presented increases in microbial CUE (17.8%, 36.9% and 25.0%, respectively), rB (43.7%, 39.7% and 10.8%, respectively), MBC (114.8%, 81.1% and 122.9%, respectively), and MNC content (47.0%, 22.2% and 21.6%, respectively). Random forest analysis suggested that SOC accumulation is controlled mainly by microbial physiological traits rather than other factors including environmental variables. Specifically, microbial CUE and turnover rates increased in old-aged forest, resulting in higher MBC and MNC contents, which in turn led to SOC accumulation. Moreover, the effects of plant and soil properties on SOC storage are regulated mainly by microbial-physiological parameters and the size of microbial C pools. Our findings provide valuable insights into the microbial mechanisms underlying SOC storage in old-aged forest.
Journal Article