[Temporal and Spatial Distribution, Utilization Status, and Carbon Emission Reduction Potential of Straw Resources in China].

Based on the crop yield data of China and each region from 1981 to 2020 (excluding data from Hong Kong, Macao, and Taiwan), by using the grain-straw ratio method, this study estimated the total amount of crop straw and collectable amount of crops, including corn, rice, wheat, other cereals, cotton, rapeseeds, peanuts, beans, tubers, sesame, fiber crops, sugarcane, and beetroots, and the spatial and temporal distribution characteristics of resource density and per capita resources of crop straw were analyzed. This study analyzed the current utilization mode, development, and change of crop straw in China. Finally, we used the life circle assessment (LCA) method to estimate the carbon emission reduction potential of biochar prepared from crop straw. The main findings were:from 1981 to 2020, the temporal distribution trend of theoretical crop straw resources and collectable straw resources in China generally showed a steady growth trend, and the two increased from 3.33×108 t and 3.04×108 t in 1981 to the highest values of 7.70×108 t and 6.63×108 t in 2020, with a net increase of 4.37×108 t and 3.59×108 t, respectively. The net increase in rice, wheat, and corn straw resources was 3.69×108t, accounting for between 77% and 85% of the total crop straw and always occupying the main position of straw resources in China. The proportion of wheat straw in the total amount of straw was maintained at approximately 20%, rice straw resources decreased from 44% to 28.4%, and corn straw increased from 19.9% to 34.2% from 1981 to 2020. In 2020, the total theoretical resources of crop straw in China were 7.72×108 t, and the source structures were:rice 28.4%, wheat 21.45%, corn 31.45%, other cereals 1.4%, beans 3.4%, tubers 0.82%, cotton 2.28%, peanuts 2.97%, rapeseeds 3.4%, sesame 0.12%, fiber crops 0.06%, beetroots 0.67%, and sugarcane 0.84%. As to the spatial distribution of crop straw resources in China in 2020, the locations with straw resources ≥ 60 million tons included Heilongjiang, Henan, and Shandong, of which Henan had as much as 88.56 million tons; those with between 40 million and 60 million tons included Hebei, Inner Mongolia, Jiangsu, and Anhui; those with between 20 million and 40 million tons included Liaoning, Jilin, Jiangxi, Hubei, Hunan, Sichuan, Yunnan, and Xinjiang; and the straw resources in the rest of the region were below 20 million tons. Rice straw was mostly distributed in the middle and lower reaches of the Yangtze River and the Northeast region, of which the amount of Heilongjiang rice straw was the largest, with 31.86 million tons; wheat straw was mainly distributed in North China, with Henan having the most abundant resources (48.04 million tons). Corn straw was mainly distributed in Northeast China and North China, of which Heilongjiang and Inner Mongolia corn straw resources were relatively rich, with 33.18 million tons and 29.90 million tons, respectively. Crop straw resource density and per capita resources were shared in 2020 in China. The average density of crop straw resources in China was 4.61 t·hm-2, and the average densities of crop straw resources in various agricultural areas were 5.39 t·hm-2 in Northeast China, 5.42 t·hm-2 in North China, 4.45 t·hm-2 in the Mengxin Region, 4.44 t·hm-2 in the middle and lower reaches of the Yangtze River, 3.92 t·hm-2in Tibet, 3.40 t·hm-2 in the Loess Plateau, 3.08 t·hm-2 in South China, and 2.91 t·hm-2 in Southwest China. The average per capita share of straw resources was 0.55 t. The average values of per capita straw resources in each region were:1.46 t in the Northeast area, 1.20 t in the Mengxin Region, 0.47 t in North China, 0.44 t in the middle and lower reaches of the Yangtze River, 0.40 t in the Loess Plateau, 0.37 t in the Southwest area, 0.33 t in the Qinghai-Tibet area, and 0.20 t in the South China area. The utilization of crop straw in China was diversified. Fertilizer and feed were the main utilizations, accounting for 62.1% and 15.4%, respectively. In 2020, collectable crop straw resources for the preparation of biochar totaled 2.04×108 t in China. Renewable energy replaced fossil fuels in the process of preparing biochar, which could reduce CO2e(CO2e:CO2 equivalent) emissions by 1.45×108 t. Biochar could sequester approximately 4.63×108 t of CO2e; biochar application was able to reduce chemical fertilizer application to achieve a CO2 emission reduction of 8.58×105 t; and biochar application could promote crop yield in order to reduce CO2e emissions by approximately 7.77×106 t. The inhibition of N2, respectively. In the process of biochar preparation and application, the total greenhouse gas emission was 3.32×107 t, and the net greenhouse effect emission reduction reached 5.86×108 t, i.e., it could sequester 0.88 t CO2e per ton of raw materials. The net greenhouse gas emission reduction of unused straw was 6.73×107 t in 2020. With the continuous harvest of grain crops in China, the potential of biochar preparation and carbon sequestration will increase yearly. Using crop straw to prepare biochar has great potential and will be one of the most effective ways to achieve carbon emission reduction in agriculture. It is suggested that government departments should pay attention to the preparation of biochar, support the field experiments of biochar application effects after applying soil on policy and funds, and then introduce relevant biochar standards to ensure the scientific application of biochar prepared by crop straw according to local conditions, so as to achieve the dual benefits of carbon emission reduction and soil remediation and yield increase.

Rhizobium terrae sp. nov., Isolated from an Oil-Contaminated Soil in China.

A Gram-stain-negative, facultative aerobic, non-spore-forming, non-motile, non-flagellated, rod-shaped bacterium, designated strain NAU-18T was isolated from an oil-contaminated soil in China. Strain NAU-18T could grow at 10-42 °C (optimum, 30 °C), at pH 5.0-8.0 (optimum, 7.0) and in the presence of 0-2.0% (w/v) NaCl (optimum, 0.5% NaCl in R2A). The predominant fatty acids were C18:1ω7c (71.2%) and Summed feature 2 (5.1%), representing 76.3% of the total fatty acids. The major respiratory quinones were Q9 and Q10. The DNA G + C content of strain NAU-18T was 61.4 mol% based on its draft genome sequence. Genome annotation of strain NAU-18T predicted the presence of 6668 genes, of which 6588 are coding proteins and 80 are RNA genes. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain NAU-18T was a member of the genus Rhizobium and showed 96.93% (with 93.2% coverage) and 96.81% (with 100% coverage) identities with those of Neorhizobium alkalisoli CCBAU 01393T and Rhizobium oryzicola ZYY136T, respectively. In the phylogenetic analysis, strain NAU-18T and R. oryzicola ZYY136T are consistently placed in the same branch. Strain NAU-18T represents a novel species within the genus Rhizobium, for which the name Rhizobium terrae sp. nov. is proposed, with the type strain NAU-18T (=KCTC 62418T = CCTCC AB 2018075T).

Rhizorhabdus dicambivorans sp. nov., a dicamba-degrading bacterium isolated from compost.

Strain Ndbn-20T, a Gram-staining-negative, non-spore-forming bacterium, was isolated from compost of plant litter. The strain was able to degrade dicamba. Phylogenetic analysis based on 16S rRNA gene sequences indicated that Ndbn-20Trepresented a member of the family Sphingomonadaceae of the Alphaproteobacteria and showed high sequence similarities to Rhizorhabdusargentea SP1T (98.8 %), Sphingomonaswittichii RW1T (97.9 %), Sphingomonasstarnbergensis 382T (97.7 %) and Sphingomonashistidinilytica UM2T (97.7 %). However, the strain showed low DNA sequence relatedness with R. argentea SP1T (45.6±1.9 %), S. wittichii RW1T (33.5±2.3 %), S.histidinilytica UM2T (39.4±3.6 %) and S. starnbergensis382T (42.1±4.1 %). Ndbn-20T possessed Q-10 as the predominant ubiquinone, spermidine as the major polyamine, and summed feature 8 (comprising C18 : 1ω7c/C18 : 1ω6c), summed feature 3 (comprising C16 : 1ω7c/C16 : 1ω6c), C17 : 1ω6c, C16 : 0 and C14 : 02-OH as the major fatty acids (>5 % of the total). The profile of polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, glycolipid, sphingoglycolipid, phosphatidyldimethylethanolamine and phosphatidylglycerol. The DNA G+C content was 65.4 mol%. Based on a polyphasic taxonomic analysis, strain Ndbn-20T is proposed to represent a novel species of the genus Rhizorhabdus, with the proposed name of Rhizorhabdus dicambivorans sp. nov. The type strain is Ndbn-20T (=CCTCC AB 2016143=KACC 18661).

Tahibacter caeni sp. nov., isolated from activated sludge.

A Gram-reaction-negative, aerobic, rod-shaped, non-spore-forming, non-motile bacterial strain, designated BUT-6(T), was isolated from activated sludge of a wastewater-treatment facility. The strain grew at 15-35 °C (optimum 30 °C), pH 4.0-10.0 (optimum pH 7.0) and 0-3.0 % (w/v) NaCl (optimum 1.0 %). Phylogenetic analysis based on 16S rRNA sequences showed that strain BUT-6(T) was most closely related to Tahibacter aquaticus PYM5-11(T) (98.6 % similarity). However, the DNA-DNA relatedness between strain BUT-6(T) and T. aquaticus PYM5-11(T) was 47.1 %. The major fatty acids (>10 % of total fatty acids) of strain BUT-6(T) were iso-C15 : 0, iso-C17 : 1ω9c and iso-C17 : 0. The major respiratory quinone was ubiquinone Q-8. The profile of polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylmethylethanolamine, an unidentified aminophospholipid, three unknown aminolipids and unidentified phospholipids. The DNA G+C content of strain BUT-6(T) was 71.7 mol%. On the basis of the data from the polyphasic taxonomic study presented, strain BUT-6(T) is considered to represent a novel species of the genus Tahibacter, for which the name Tahibacter caeni sp. nov. is proposed. The type strain is BUT-6(T) ( = CCTCC AB 2013266(T) = KACC 17139(T)).

Lysobacter caeni sp. nov., isolated from the sludge of a pesticide manufacturing factory.

Strain BUT-8(T), a Gram-stain-negative, non-motile and rod-shaped aerobic bacterium, was isolated from the activated sludge of a herbicide-manufacturing wastewater treatment facility. Comparative 16S rRNA gene sequence analysis revealed that strain BUT-8(T) clustered with species of the genus Lysobacter and was closely related to Lysobacter ruishenii DSM 22393(T) (98.3 %) and Lysobacter daejeonensis KACC 11406(T) (98.7 %). The DNA G+C content of the genomic DNA was 70.6 mol%. The major respiratory quinone was ubiquinone-8, and the major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and an aminolipid. The major cellular fatty acids were iso-C15 : 0, iso-C16 : 0, iso-C17 : 0, iso-C11 : 0, iso-C11 : 0 3OH and summed feature 9 (comprising iso-C17 : 1ω9c and/or C16 : 010-methyl). The DNA-DNA relatedness between strain BUT-8(T) and its closest phylogenetic neighbours was below 70 %. Phylogenetic, chemotaxonomic and phenotypic results clearly demonstrated that strain BUT-8(T) belongs to the genus Lysobacter and represents a novel species for which the name Lysobacter caeni sp. nov. is proposed. The type strain is BUT-8(T) ( = CCTCC AB 2013087(T) = KACC 17141(T)).

Pseudoxanthobacter liyangensis sp. nov., isolated from dichlorodiphenyltrichloroethane-contaminated soil.

An aerobic, Gram-stain negative, pale, rod-shaped, nitrogen-fixing bacterial strain, DDT-3(T), was isolated from dichlorodiphenyltrichloroethane-contaminated soil in Liyang, PR China. Strain DDT-3(T) grew at temperatures ranging from 20 to 40 °C (optimum 30-37 °C) and a pH of between 5.0 and 10.0 (optimum pH 7.0-8.0). The G+C content of the total DNA was 70.1 mol%. The 16S rRNA gene sequence of strain DDT-3(T) showed the highest similarity to that of Pseudoxanthobacter soli CC4(T) (99.6%), followed by Kaistia dalseonensis B6-8(T) (93.3%), Kaistia soli 5YN9-8(T) (93.0%) and Amorphus orientalis YIM D10(T) (93.0%). Strain DDT-3(T) showed less than 92.6 % similarity with other species of the family Xanthobacteraceae. The major cellular fatty acids of strain DDT-3(T) were C19:0 cyclo ω8c (42.6%), C16:0 (33.2%) and C18:1ω7c (10.0%). The only respiratory quinone was ubiquinone Q-10. The characteristic diamino acid of the peptidoglycan was meso-diaminopimelic acid. The major polar lipids were glycolipid, lipid, phosphatidylcholine, aminolipid, phosphatidylmethylethanolamine, diphosphatidylglycerol and phosphatidylglycerol. The polyamine profile consisted of major amounts of putrescine (92.9%) and minor amounts of spermidine (5.0%) and spermine (2.1%). These chemotaxonomic data support the affiliation of strain DDT-3(T) with the genus Pseudoxanthobacter. The DNA-DNA hybridization value between strain DDT-3(T) and strain CC4(T) was 47.8% (reciprocal 44.3%). DNA-DNA hybridization data as well as the biochemical and physiological characteristics strongly supported the genotypic and phenotypic differentiation of strain DDT-3(T) and strain CC4(T). Strain DDT-3(T), therefore, represents a novel species of the genus Pseudoxanthobacter, for which the name Pseudoxanthobacter liyangensis sp. nov. is proposed. The type strain is DDT-3(T) ( = KACC 16601(T) = CCTCC AB 2013167(T)).

Knockout of fatty acid desaturase genes in Pichia pastoris GS115 and its effect on the fatty acid biosynthesis and physiological consequences.

Unsaturated fatty acids (UFAs), including oleic acid (OA, C18:1n-9), linoleic acid (LA, C18:2n-6) and α-linolenic acid (ALA, C18:3n-3), are major components of membrane lipids in Pichia pastoris GS115. In order to clarify the biosynthesis pathway of UFAs on the molecular level and investigate their possible roles in growth and development of this strain, we here report modified strains with disrupted desaturase gene by homologous recombination. Gas chromatography analysis of fatty acid composition in the corresponding mutants confirmed that ∆(12)-desaturase encoded by Fad12 was responsible for the formation of LA, and ALA was synthesized by ∆(15)-desaturase encoded by Fad15. Simultaneous deletion of Fad9A and Fad9B was lethal and supplementation of OA could restore growth, indicating that possibly both Fad9A and Fad9B encoded ∆(9)-desaturase that converted SA into OA. Phenotypic analysis demonstrated that wild type and Fad15 mutant grew at almost the same rate, Fad12 mutant grew much slower than these two strains. Moreover, OA was positively correlated to cold tolerance and ethanol tolerance of GS115, whereas LA and ALA did not affect cold tolerance and ethanol tolerance of it. In addition, we showed that tolerance of GS115 to high concentration of methanol was independent of these three UFAs.

Effects of different carbon sources on the growth, fatty acids production, and expression of three desaturase genes of Mortierella alpina ATCC 16266.

On the molecular and biochemical levels, the effects of different carbon sources on biomass production, fatty acid biosynthesis, and gene expression of three desaturases were investigated in Mortierella alpina ATCC 16266, at a stationary phase, which is an important filamentous fungus capable of producing various polyunsaturated fatty acids (PUFAs). The maximum mycelial biomass was achieved using sucrose as carbon source. However, the highest productivity of total lipids was shown to be no biomass associated. In addition, glucose was the preferred carbon source for the expression of three desaturase genes compared to others, but the change at the corresponding fatty acid product's level of these desaturase genes was not in accordance with the change measured at the mRNA level among those carbon sources that we utilized. Significant discrepancies between the mRNA expression and the product abundance may indicate post-transcriptional regulatory mechanisms of these desaturases.