scholarly journals Screening of Cellulolytic Bacteria from Rotten Wood of Qinling (China) for Biomass Degradation and Cloning of Cellulases from Bacillus methylotrophicus

2019 ◽  
Author(s):  
Lingling Ma ◽  
Yingying Lu ◽  
Hong Yan ◽  
Xin Wang ◽  
Yanglei Yi ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Wheat Straw ◽  
Cellulose Degradation ◽  
Good Effect ◽  
Qinling Mountains ◽  
Cellulolytic Bacteria ◽  
Biomass Degradation ◽  
Bacillus Methylotrophicus ◽  
Rotten Wood ◽  
Degradation Effect

Abstract Background Cellulosic biomass degradation still needs to be paid more attentions as bioenergy is the most likely to replace fossil energy in the future, and more evaluable cellulolytic bacteria isolation will lay a foundation for this filed. Qinling Mountains have unique biodiversity, acting as promising source of cellulose-degrading bacteria exhibiting noteworthy properties. Therefore, the aim of this work was to find potential cellulolytic bacteria and verify the possibility of the cloning of cellulases from the selected powerful bacteria. Results In present study, 55 potential cellulolytic bacteria were screened and identified from the rotten wood of Qinling Mountains. Based on the investigation of cellulase activities and degradation effect on different cellulose substrates, Bacillus methylotrophicus 1EJ7, Bacillus subtilis 1AJ3 and Bacillus subtilis 3BJ4 were further applied to hydrolyze wheat straw, corn stover and switchgrass, and the results suggested that B. methylotrophicus 1EJ7 was the most preponderant bacterium, and which also indicated that Bacillus was the main cellulolytic bacteria in rotten wood. Furthermore, scanning electron microscopy (SEM) and X-ray diffraction analysis of micromorphology and crystallinity of wheat straw also verified the significant hydrolyzation. With ascertaining the target sequence of cellulase β-glucosidase (243 aa) and endoglucanase (499 aa) were successfully heterogeneously cloned and expressed from B. methylotrophicus 1EJ7, and which performed a good effect on cellulose degradation with enzyme activity of 1670.15±18.94 U/mL and 0.130±0.002 U/mL, respectively. In addition, based on analysis of amino acid sequence, it found that β-glucosidase were belonged to GH16 family, and endoglucanase was composed of GH5 family catalytic domain and a carbohydrate-binding module of CBM3 family. Conclusions Based on the screening, identification and cellulose degradation effect evaluation of cellulolytic bacteria from rotten wood of Qinling Mountains, it found that Bacillus were the predominant species among the isolated strains, and B. methylotrophicus 1EJ7 performed best on cellulose degradation. Meanwhile, the β-glucosidase and endoglucanase were successfully cloned and expressed from B. methylotrophicus for the first time, which provided new materials of both strain and the recombinant enzymes for the study of cellulose degradation and its application in industry.

scholarly journals Screening of cellulolytic bacteria from rotten wood of Qinling (China) for biomass degradation and cloning of cellulases from Bacillus methylotrophicus

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Lingling Ma ◽  
Yingying Lu ◽  
Hong Yan ◽  
Xin Wang ◽  
Yanglei Yi ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Wheat Straw ◽  
Cellulose Degradation ◽  
Good Effect ◽  
Qinling Mountains ◽  
Cellulolytic Bacteria ◽  
Biomass Degradation ◽  
Bacillus Methylotrophicus ◽  
Rotten Wood ◽  
Degradation Effect

Abstract Background Cellulosic biomass degradation still needs to be paid more attentions as bioenergy is the most likely to replace fossil energy in the future, and more evaluable cellulolytic bacteria isolation will lay a foundation for this filed. Qinling Mountains have unique biodiversity, acting as promising source of cellulose-degrading bacteria exhibiting noteworthy properties. Therefore, the aim of this work was to find potential cellulolytic bacteria and verify the possibility of the cloning of cellulases from the selected powerful bacteria. Results In present study, 55 potential cellulolytic bacteria were screened and identified from the rotten wood of Qinling Mountains. Based on the investigation of cellulase activities and degradation effect on different cellulose substrates, Bacillus methylotrophicus 1EJ7, Bacillus subtilis 1AJ3 and Bacillus subtilis 3BJ4 were further applied to hydrolyze wheat straw, corn stover and switchgrass, and the results suggested that B. methylotrophicus 1EJ7 was the most preponderant bacterium, and which also indicated that Bacillus was the main cellulolytic bacteria in rotten wood. Furthermore, scanning electron microscopy (SEM) and X-ray diffraction analysis of micromorphology and crystallinity of wheat straw also verified the significant hydrolyzation. With ascertaining the target sequence of cellulase β-glucosidase (243 aa) and endoglucanase (499 aa) were successfully heterogeneously cloned and expressed from B. methylotrophicus 1EJ7, and which performed a good effect on cellulose degradation with enzyme activity of 1670.15 ± 18.94 U/mL and 0.130 ± 0.002 U/mL, respectively. In addition, based on analysis of amino acid sequence, it found that β-glucosidase were belonged to GH16 family, and endoglucanase was composed of GH5 family catalytic domain and a carbohydrate-binding module of CBM3 family. Conclusions Based on the screening, identification and cellulose degradation effect evaluation of cellulolytic bacteria from rotten wood of Qinling Mountains, it found that Bacillus were the predominant species among the isolated strains, and B. methylotrophicus 1EJ7 performed best on cellulose degradation. Meanwhile, the β-glucosidase and endoglucanase were successfully cloned and expressed from B. methylotrophicus for the first time, which provided new materials of both strain and the recombinant enzymes for the study of cellulose degradation and its application in industry.

scholarly journals Screening of Cellulolytic Bacteria from Rotten Wood of Qinling (China) for Biomass Degradation and Cloning of Cellulases from Bacillus methylotrophicus

2019 ◽  
Author(s):  
Lingling Ma ◽  
Yingying Lu ◽  
Hong Yan ◽  
Xin Wang ◽  
Yanglei Yi ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Wheat Straw ◽  
Cellulose Degradation ◽  
Good Effect ◽  
Qinling Mountains ◽  
Cellulolytic Bacteria ◽  
Biomass Degradation ◽  
Bacillus Methylotrophicus ◽  
Rotten Wood ◽  
Degradation Effect

Abstract Background Cellulosic biomass degradation still needs to be paid more attentions as bioenergy is the most likely to replace fossil energy in the future, and more evaluable cellulolytic bacteria isolation will lay a foundation for this filed. Qinling Mountains have unique biodiversity, acting as promising source of cellulose-degrading bacteria exhibiting noteworthy properties. Therefore, the aim of this work was to find potential cellulolytic bacteria and verify the possibility of the cloning of cellulases from the selected powerful bacteria. Results In present study, 55 potential cellulolytic bacteria were screened and identified from the rotten wood of Qinling Mountains. Based on the investigation of cellulase activities and degradation effect on different cellulose substrates, Bacillus methylotrophicus 1EJ7, Bacillus subtilis 1AJ3 and Bacillus subtilis 3BJ4 were further applied to hydrolyze wheat straw, corn stover and switchgrass, and the results suggested that B. methylotrophicus 1EJ7 was the most preponderant bacterium, and which also indicated that Bacillus was the main cellulolytic bacteria in rotten wood. Furthermore, scanning electron microscopy (SEM) and X-ray diffraction analysis of micromorphology and crystallinity of wheat straw also verified the significant hydrolyzation. With ascertaining the target sequence of cellulase β-glucosidase (243 aa) and endoglucanase (499 aa) were successfully heterogeneously cloned and expressed from B. methylotrophicus 1EJ7, and which performed a good effect on cellulose degradation with enzyme activity of 1670.15±18.94 U/mL and 0.130±0.002 U/mL, respectively. In addition, based on analysis of amino acid sequence, it found that β-glucosidase were belonged to GH16 family, and endoglucanase was composed of GH5 family catalytic domain and a carbohydrate-binding module of CBM3 family. Conclusions Based on the screening, identification and cellulose degradation effect evaluation of cellulolytic bacteria from rotten wood of Qinling Mountains, it found that Bacillus were the predominant species among the isolated strains, and Bacillus methylotrophicus 1EJ7 performed best on cellulose degradation. Meanwhile, the β-glucosidase and endoglucanase were successfully cloned and expressed from Bacillus methylotrophicus for the first time, which provided new materials of both strain and the recombinant enzymes for the study of cellulose degradation and its application in industry.

scholarly journals Cellulolytic Bacteria Screened from Qinling (China) for Biomass Degradation and Cellulases First Cloned from Bacillus methylotrophicus

2019 ◽  
Author(s):  
Lingling Ma ◽  
Yingying Lu ◽  
Hong Yan ◽  
Xin Wang ◽  
Yanglei Yi ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Bacillus Subtilis ◽  
Carbon Source ◽  
Wheat Straw ◽  
Corn Stover ◽  
Sugar Content ◽  
Qinling Mountains ◽  
Cellulolytic Bacteria ◽  
Biomass Degradation ◽  
Bacillus Methylotrophicus

Abstract Background Cellulosic biomass degradation still needed more studies while bioenergy is becoming mainly energy in future and more evaluate bacteria isolation laid a foundation of further study. Qinling Mountains have unique biodiversity, acting as promising source of cellulose-degrading bacteria exhibiting noteworthy properties. The aim of this work was to find potential cellulolytic bacteria in depredating multiform carbon source cellulose substrate. Results In this study, 55 potential cellulolytic bacteria screened out and were identified. Based on the results of the investigation of cellulase activities and reducing sugar content via different carbon substrate effect, Bacillus methylotrophicus 1EJ7, Bacillus subtilis 1AJ3 and Bacillus subtilis 3BJ4 were further taken to hydrolyze wheat straw, corn stover and switchgrass, suggesting that B. methylotrophicus 1EJ7 was the most preponderant bacterium, obtaining highest sugar content (95mg/100mL) in switchgrass, wheat straw and corn stover. Scanning electron microscopy (SEM) and X-ray diffraction results of wheat straw surface and crystallinity indicated the hydrolyzation. By ascertaining the target sequence of cellulase for the cloning and expression in an economical and convenient manner, the genes of β-glucosidase (243 aa) and endoglucanase (499 aa) of B. methylotrophicus 1EJ7. Recombinant β-glucosidase from GH16 family and enzyme activity was 1670.15±18.94 U/mL. Endoglucanase consist of GH5 family catalytic domain and a carbohydrate-binding module belongs to CBM3 family and enzyme activity was 0.130±0.002 U/mL. Conclusions Screened, identified the cellulolytic bacteria from rotten wood of Qinling Mountains and explored their ability in degrading different carbon source cellulose substrate, including purified and natural carbon sources. Bacillus were the predominant species among the isolated strains, and Bacillus methylotrophicus 1EJ7 performant well on cellulose degradation. In the meantime, the β-glucosidase and endoglucanase were successfully cloned and expressed from Bacillus methylotrophicus for the first time. The strain and the recombinant enzyme have potential application in industrial production.

Characterization of enriched aerotolerant cellulose-degrading communities for biofuels production using differing selection pressures and inoculum sources

2013 ◽  
Vol 59 (10) ◽  
pp. 679-683 ◽  
Author(s):  
Scott Wushke ◽  
David B. Levin ◽  
Nazim Cicek ◽  
Richard Sparling
Keyword(s):  
Consolidated Bioprocessing ◽  
Ethanol Yield ◽  
Cellulose Degradation ◽  
16S Rrna Gene Sequencing ◽  
Rrna Gene ◽  
Strictly Anaerobic ◽  
Cellulolytic Bacteria ◽  
Moderately Thermophilic ◽  
Rotten Wood ◽  
Gradient Gel Electrophoresis

Ethanol production from direct cellulose fermentation has mainly been described as a strictly anaerobic process. The use of air-tolerant organisms or consortia for this process would reduce the need for prereduction of the medium and also permit continuous feed of aerobic feedstock. To this end, moderately thermophilic (60 °C) consortia of fermentative, cellulolytic bacteria were enriched from 3 distinct environments (manure, marsh, and rotten wood) from a farm in southeast Saskatchewan, Canada. Community phenotypic and metabolic profiles were characterized. Selection methods included direct plating under an aerobic atmosphere and repeated passaging; the methods were designed to select for robust, stable aerotolerant cellulose-degrading communities. Several of the isolated communities exhibited an increase in total cellulose degradation and total ethanol yield when compared with a monoculture of Clostridium thermocellum DSMZ 1237. Owing to stringent selection conditions, low diversity enrichments were found, and many appeared to be binary cultures via density gradient gel electrophoresis analysis. On the basis of 16S rRNA gene sequencing, aerobic conditions selected for a mix of organisms highly related to C. thermocellum and Geobacillus species, while anaerobic conditions led to the development of consortia containing strains related to C. thermocellum with strains from either the genus Geobacillus or the genus Thermoanaerobacter. The presence of a Geobacillus-like species appeared to be a prerequisite for aerotolerance of the cellulolytic enrichments, a highly desired phenotype in lignocellulosic consolidated bioprocessing.

scholarly journals CELLULOLYTIC BACTERIA MANGROVE LEAF LITTER IN BANGKA ISLAND

2018 ◽  
Vol 9 (1) ◽  
pp. 06-11
Author(s):  
Ardiansyah Kurniawan ◽  
Asep Awaludin Prihanto ◽  
Suci Puspitasari ◽  
Andi Kurniawan ◽  
Euis Asriani ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Leaf Litter ◽  
Agar Medium ◽  
Cellulose Degradation ◽  
Bacterial Isolates ◽  
Cellulolytic Bacteria ◽  
Clear Zone ◽  
Biochemical Tests ◽  
Positive Isolate ◽  
Degradation Ability

The study aimed to obtain isolate of cellulolytic bacteria from leaf litter on mangrove in Bangka Island. Sampling was conducted on mangroves in Sungailiat, Bangka and Tukak Sadai, South Bangka district. The isolation was carried out using 1% enriched agarmedia of Carboxymetyl Cellulose (CMC). The bacterial isolates were tested with cellulolytic growth on 1% enriched CMC agar medium and lugol added at 72 hours. The clear zone resultingindicates cellulose degradation ability. The positive isolate of  cellulolyticwas identified by biochemical tests. 1 of 5 isolates in Sungailiat positive cellulolytic mangroves and identified as Bacillus subtilis. 2 of 5 isolates in mangrove Tukak Sadai is positive as a cellulolytic bacteria and identified as Staphylococcus saproviticus and Bacillus cereus.

scholarly journals Optimization of β-1,4-Endoxylanase Production by an Aspergillus niger Strain Growing on Wheat Straw and Application in Xylooligosaccharides Production

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2527
Author(s):  
Zahra Azzouz ◽  
Azzeddine Bettache ◽  
Nawel Boucherba ◽  
Alicia Prieto ◽  
Maria Jesus Martinez ◽  
...  
Keyword(s):  
Aspergillus Niger ◽  
Wheat Straw ◽  
Plant Biomass ◽  
Residual Activity ◽  
Exchange Chromatography ◽  
Glycosyl Hydrolases ◽  
Biomass Degradation ◽  
Xylan Hydrolysis ◽  
Rsm Optimization ◽  
Single Carbon Source

Plant biomass constitutes the main source of renewable carbon on the planet. Its valorization has traditionally been focused on the use of cellulose, although hemicellulose is the second most abundant group of polysaccharides on Earth. The main enzymes involved in plant biomass degradation are glycosyl hydrolases, and filamentous fungi are good producers of these enzymes. In this study, a new strain of Aspergillus niger was used for hemicellulase production under solid-state fermentation using wheat straw as single-carbon source. Physicochemical parameters for the production of an endoxylanase were optimized by using a One-Factor-at-a-Time (OFAT) approach and response surface methodology (RSM). Maximum xylanase yield after RSM optimization was increased 3-fold, and 1.41- fold purification was achieved after ultrafiltration and ion-exchange chromatography, with about 6.2% yield. The highest activity of the purified xylanase was observed at 50 °C and pH 6. The enzyme displayed high thermal and pH stability, with more than 90% residual activity between pH 3.0–9.0 and between 30–40 °C, after 24 h of incubation, with half-lives of 30 min at 50 and 60 °C. The enzyme was mostly active against wheat arabinoxylan, and its kinetic parameters were analyzed (Km = 26.06 mg·mL−1 and Vmax = 5.647 U·mg−1). Wheat straw xylan hydrolysis with the purified β-1,4 endoxylanase showed that it was able to release xylooligosaccharides, making it suitable for different applications in food technology.

scholarly journals Torrefaction of Woody and Agricultural Biomass: Influence of the Presence of Water Vapor in the Gaseous Atmosphere

Processes ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 30
Author(s):  
María González Martínez ◽  
Estéban Hélias ◽  
Gilles Ratel ◽  
Sébastien Thiéry ◽  
Thierry Melkior
Keyword(s):  
Water Vapor ◽  
Water Content ◽  
Wheat Straw ◽  
Beech Wood ◽  
High Water ◽  
High Water Content ◽  
Biomass Degradation ◽  
Moist Atmosphere ◽  
Thermochemical Transformation ◽  
Degradation Reactions

Biomass preheating in torrefaction at an industrial scale is possible through a direct contact with the hot gases released. However, their high water-content implies introducing moisture (around 20% v/v) in the torrefaction atmosphere, which may impact biomass thermochemical transformation. In this work, this situation was investigated for wheat straw, beech wood and pine forest residue in torrefaction in two complementary experimental devices. Firstly, experiments in chemical regime carried out in a thermogravimetric analyzer (TGA) showed that biomass degradation started from lower temperatures and was faster under a moist atmosphere (20% v/v water content) for all biomass samples. This suggests that moisture might promote biomass components’ degradation reactions from lower temperatures than those observed under a dry atmosphere. Furthermore, biomass inorganic composition might play a role in the extent of biomass degradation in torrefaction in the presence of moisture. Secondly, torrefaction experiments on a lab-scale device made possible to assess the influence of temperature and residence time under dry and 100% moist atmosphere. In this case, the difference in solid mass loss between dry and moist torrefaction was only significant for wheat straw. Globally, an effect of water vapor on biomass transformation through torrefaction was observed (maximum 10%db), which appeared to be dependent on the biomass type and composition.

scholarly journals Efficient Plant Biomass Degradation by Thermophilic Fungus Myceliophthora heterothallica

2012 ◽  
Vol 79 (4) ◽  
pp. 1316-1324 ◽  
Author(s):  
Joost van den Brink ◽  
Gonny C. J. van Muiswinkel ◽  
Bart Theelen ◽  
Sandra W. A. Hinz ◽  
Ronald P. de Vries
Keyword(s):  
Wheat Straw ◽  
Plant Biomass ◽  
Hydrolytic Enzymes ◽  
Reaction Times ◽  
Giant Reed ◽  
Thermophilic Fungi ◽  
Biomass Degradation ◽  
Thermostable Enzymes ◽  
Content Type

ABSTRACTRapid and efficient enzymatic degradation of plant biomass into fermentable sugars is a major challenge for the sustainable production of biochemicals and biofuels. Enzymes that are more thermostable (up to 70°C) use shorter reaction times for the complete saccharification of plant polysaccharides compared to hydrolytic enzymes of mesophilic fungi such asTrichodermaandAspergillusspecies. The genusMyceliophthoracontains four thermophilic fungi producing industrially relevant thermostable enzymes. Within this genus, isolates belonging toM. heterothallicawere recently separated from the well-described speciesM. thermophila. We evaluate here the potential ofM. heterothallicaisolates to produce efficient enzyme mixtures for biomass degradation. Compared to the other thermophilicMyceliophthoraspecies, isolates belonging toM. heterothallicaandM. thermophilagrew faster on pretreated spruce, wheat straw, and giant reed. According to their protein profiles andin vitroassays after growth on wheat straw, (hemi-)cellulolytic activities differed strongly betweenM. thermophilaandM. heterothallicaisolates. Compared toM. thermophila,M. heterothallicaisolates were better in releasing sugars from mildly pretreated wheat straw (with 5% HCl) with a high content of xylan. The high levels of residual xylobiose revealed that enzyme mixtures ofMyceliophthoraspecies lack sufficient β-xylosidase activity. Sexual crossing of twoM. heterothallicashowed that progenies had a large genetic and physiological diversity. In the future, this will allow further improvement of the plant biomass-degrading enzyme mixtures ofM. heterothallica.

scholarly journals Ethanol production using vegetable peels medium and the effective role of cellulolytic bacterial (Bacillus subtilis) pre-treatment

F1000Research ◽  
2018 ◽  
Vol 7 ◽  
pp. 271
Author(s):  
Salman Khan Promon ◽  
Wasif Kamal ◽  
Shafkat Shamim Rahman ◽  
M. Mahboob Hossain ◽  
Naiyyum Choudhury
Keyword(s):  
Bacillus Subtilis ◽  
Ethanol Production ◽  
Energy Demand ◽  
Biochemical Characterization ◽  
Raw Materials ◽  
Maximum Yield ◽  
Clean Energy ◽  
Raw Material ◽  
Cellulolytic Bacteria ◽  
Alcohol Production

Background: The requirement of an alternative clean energy source is increasing with the elevating energy demand of modern age. Bioethanol is considered as an excellent candidate to satiate this demand.Methods:Yeast isolates were used for the production of bioethanol using cellulosic vegetable wastes as substrate. Efficient bioconversion of lignocellulosic biomass into ethanol was achieved by the action of cellulolytic bacteria (Bacillus subtilis).  After proper isolation, identification and characterization of stress tolerances (thermo-, ethanol-, pH-, osmo- & sugar tolerance), optimization of physiochemical parameters for ethanol production by the yeast isolates was assessed. Very inexpensive and easily available raw materials (vegetable peels) were used as fermentation media. Fermentation was optimized with respect to temperature, reducing sugar concentration and pH.Results:It was observed that temperatures of 30°C and pH 6.0 were optimum for fermentation with a maximum yield of ethanol. The results indicated an overall increase in yields upon the pretreatment ofBacillus subtilis; maximum ethanol percentages for isolate SC1 obtained after 48-hour incubation under pretreated substrate was 14.17% in contrast to untreated media which yielded 6.21% after the same period. Isolate with the highest ethanol production capability was identified as members of the ethanol-producingSaccharomycesspecies after stress tolerance studies and biochemical characterization using Analytical Profile Index (API) ® 20C AUX and nitrate broth test. Introduction ofBacillus subtilisincreased the alcohol production rate from the fermentation of cellulosic materials.Conclusions:The study suggested that the kitchen waste can serve as an excellent raw material in ethanol fermentation.

scholarly journals Pengaruh Aplikasi Plant Growth Promoting Rhizobacteria terhadap Pertumbuhan dan Hasil Tanaman Bawang Merah (Allium cepa L. Aggregatum group)

Vegetalika ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 512
Author(s):  
Nanda Dwi Hafri ◽  
Endang Sulistyaningsih ◽  
Arif Wibowo
Keyword(s):  
Bacillus Subtilis ◽  
Plant Growth ◽  
Allium Cepa ◽  
Burkholderia Cepacia ◽  
Plant Growth Promoting Rhizobacteria ◽  
Bacillus Methylotrophicus ◽  
Plant Growth Promoting ◽  
Growth Promoting

Salah satu upaya penanganan penyakit moler bawang merah dilakukan melalui aplikasi Trichoderma. Aplikasi Trichoderma pada bawang merah memiliki beberapa keunggulan, yaitu mampu mensintesis hormon pertumbuhan tanaman. Terdapat jenis mikroba lain yang juga mampu meningkatkan fitohormon pada tanaman, yaitu Plant Growth Promoting Rhizobacteria (PGPR). Tujuan dari penelitian ini adalah untuk mengetahui dan menentukan isolat PGPR yang memiliki pengaruh paling baik terhadap pertumbuhan dan hasil bawang merah varietas Crok Kuning di lahan sawah. Penelitian ini menggunakan Rancangan Acak Kelompok Lengkap (RAKL) faktor tunggal dengan tiga blok sebagai ulangan. Faktor perlakuan yang digunakan adalah lima isolat PGPR, yaitu: Bp.25.7 Bacillus subtilis, BrSG.5 Bacillus amyloliquofaciens, Bp.25.2 Bacillus methylotrophicus, BrsM.4 Burkholderia cepacia, danBp.25.6 Bacillus amyloliquofaciens dengan dua kontrol, yaitu kontrol positif berupa Trichoderma dan kontrol negatif tanpa aplikasi perlakuan. Hasil penelitian menunjukkan bahwa pemberian perlakuan isolat Bp.25.2 Bacillus methylotrophicus pada bawang merah menyebabkan Laju Asimilasi Bersih (LAB) bawang merah lebih tinggi dibandingkan dengan pemberian perlakuan empat isolat PGPR lainnya maupun kontrol, tetapi sama baiknya dengan pemberian perlakuan Trichoderma. LAB yang tinggi menyebabkan Laju Pertumbuhan Tanaman (LPT) bawang merah dengan pemberian perlakuan Bp.25.2 Bacillus methylotrophicus yang lebih tinggi dibandingkan dengan BrSG.5 Bacillus amyloliquofaciens dan Bp.25.6 Bacillus amyloliquofaciens, tetapi sama baiknya dengan pemberian perlakuan dua isolat PGPR lainnya, kontrol, maupun Trichoderma. Pemberian aplikasi lima isolat PGPR sama baiknya dengan aplikasi Trichoderma dalam meningkatkan pertumbuhan tanaman bawang merah pada variabel luas permukaan daun dan bobot kering total dibandingkan kontrol. Peningkatan variabel pertumbuhan ini tidak diikuti oleh peningkatan variabel hasil dan produktivitas bawang merah tidak berbeda nyata antar perlakuan.

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