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The worldwide loss of date palm (Phoenix dactyliferaL.) productivity is due to the infestation of the red pest weevil (RPW). The pest makes tunnels in the tree trunk and could be followed by secondary microbial infections causing oozing of fluid with a distinct fermentation odor. This study aimed at isolation and identification of secondary invader bacteria associated with the RPW and confirmation of their potential destructive effect on the tree. Four bacterial isolates were recovered from the infested date palm tissues, and they were identified based on phenotypic characteristics using the VITEK2 system. Three out of the four isolates were identified as Pseudomonas aeruginosa, and one isolate was identified as Burkholderia cepacia. All isolates caused rot of date palm germinated seeds (up to 40%), and wilt and root rot of date palm seedlings (40–100%). Pseudomonas aeruginosa(isolate No. 3) was the most aggressive isolate that involved 40% mortality and caused 100% of root rot incidence in date palm seedlings. Burkholderia cepaciashowed the lowest degree of rot on the germinated seeds, percentage mortality, percentage root rot incidence of date palm seedlings. Pseudomonas aeruginosa(isolate No. 1) and B. cepaciacaused a high loss in the weight of date palm petioles tissues (about 10%). The study threw light on the detrimental effects of secondary invader microbes associated with the RPW infestation. The study recommended an application of an integrated management program containing both antibacterial and insecticidal preparation in the management of the RPW to avoid a further negative effect on the palm trees. The study confirms the destructive effect of secondary invader bacteria in palms.Burkholderia cepaciaand Pseudomonas aeruginosawere secondary invaders associated with red pest weevil.P. aeruginosawas an aggressive isolate involved in 40% mortality of palm seedlings.

AbstractCitric acid is a commercially valuable organic acid widely used in food, pharmaceutical, and beverage industries. In this study, 260 yeast strains were isolated from soil, bread, juices, and fruits wastes and preliminarily screened using bromocresol green agar plates for their ability to produce organic acids. Overall, 251 yeast isolates showed positive results, with yellow halos surrounding the colonies. Citric acid production by 20 promising isolates was evaluated using both free and immobilized cell techniques. Results showed that citric acid production by immobilized cells (30–40 g/L) was greater than that of freely suspended cells (8–19 g/L). Of the 20 isolates, two (KKU-L42 and KKU-L53) were selected for further analysis based on their citric acid production levels. Immobilized KKU-L42 cells had a higher citric acid production rate (62.5%), while immobilized KKU-L53 cells showed an ∼52.2% increase in citric acid production compared with free cells. The two isolates were accurately identified by amplification and sequence analysis of the 26S rRNA gene D1/D2 domain, with GenBank-based sequence comparison confirming that isolates KKU-L42 and KKU-L53 were Candida tropicalisand Pichia kluyveri, respectively. Several factors, including fermentation period, pH, temperature, and carbon and nitrogen source, were optimized for enhanced production of citric acid by both isolates. Maximum production was achieved at fermentation period of 5 days at pH 5.0 with glucose as a carbon source by both isolates. The optimum incubation temperature for citric acid production by C. tropicaliswas 32 °C, with NH4Cl the best nitrogen source, while maximum citric acid by P. kluyveriwas observed at 27 °C with (NH4)2SO4as the nitrogen source. Citric acid production was maintained for about four repeated batches over a period of 20 days. Our results suggest that apple and banana wastes are potential sources of novel yeast strains; C. tropicalisand P. kluyveriwhich could be used for commercial citric acid production.

The targeting of the current work is enhancing the supercapacitor efficiency of the magnetite nanocomposite with graphene oxide (GO) nanostructure via the addition of metal oxide nanoparticles (NPs) such as cobalt, manganese, vanadium, and zirconium for building a novel nano combination. The sol/gel method is utilized to fabricate the nanocomposites, and the potentiostat device measures the electrochemical performances. The supercapacitors of the magnetite (Fe3O4) NPs that decorate the graphene oxide (GO) surface and the modified electrode building have been examined by different tests for supercapacitor applications, and are studied via the impedance spectroscopy (EIS) data that confirm the building progress of the electron transfer and surface structure that enable it to be a favorable candidate for supercapacitors applications. The areal capacitance (Carea) of NCPs was measured and presented at 622.65 mFcm−2(GO@Fe3O4), 62.428 mFcm−2(GO@ Fe3O4.Co3O4), 388.4 mFcm−2(GO@ Fe3O4.Mn3O4), 851.1 mFcm−2(GO@Fe3O4.V4O7), 966.4 mFcm−2(GO@Fe3O4.ZrO2). The NCPs have capacitance values related to CPE (C = 9.404 nF/cm2), GO@Fe3O4(C = 40.886 nF/cm2), GO@Fe3O4.Co3O4(C = 13.17 nF/cm2), GO@Fe3O4.Mn3O4(C = 17.56 nF/cm2), GO@Fe3O4.V4O7(C = 126.9 nF/cm2), and GO@Fe3O4.ZrO2(C = 183.6 nF/cm2). By adding cobalt, manganese, vanadium, and zirconium metal oxide NPs, the new building electrodes have capacitance at 13.17, 17.56, 183.6, and 126.9 nF/cm2, respectively. The capacitance retention finished at 100 cycles is recorded and exhibited good cycle stability. From the results, the fabricated NCPS electrodes are a promising candidate for supercapacitor manufacturing applications and other applications such as water treatment.

This study aimed to evaluate the efficiency of Enterobacter cloacaePS14 and Trichoderma asperellumT34 in the control of potato wilt, caused by Ralstonia solanacearum(Smith), under greenhouse and field conditions. In vitro, the endophyte E. cloacaePS14 caused the highest reduction of the pathogen growth among 7 screened bacteria. It produced an inhibition zone as 16.9 mm compared to a specific antibiotic (20.0 mm). E. cloacaePS14 was selected as an effective antagonistic bacterium to be compared to T. asperellumstrain T34 for reduction of the disease as well as increasing the crop yield of potato plants. Both E. cloacaeand T. asperellumreduced the disease severity up to 10.7–26.5%, respectively, under greenhouse and up to 26.6–36.6%, respectively, under field conditions. The results approved that both E. cloacaeand T. asperellumincreased the yield of the crop by 20.44–40.96%, respectively. Their mode of action was indicated by suppression of the pathogen as well as induction of plant systemic resistance. The induction of systemic resistance was confirmed by increasing the total phenol and salicylic acid contents as well as increasing the activities of peroxidase, lipoxygenase, and polyphenol oxidase in potato plants than the healthy or only infected plants. Production of siderophore, indole-3-acetic acid (0.577–0.884 μM), hydrogen cyanide (2.34–3.61 μg/ml), and salicylic acid (0.436–1.488 μg/ml) was confirmed by E. cloacae PS14 and T. asperellumT34, respectively, in vitro. The study recommends the new strain E. cloacaePS14, as new endophytic effective bacteria, in the control of R. solanacearumcausing the potato wilt disease.