No abstract

The search for sustainable alternatives to the production of chemicals using renewable substrates and natural processes has been widely encouraged. Microbial surfactants or biosurfactants are surface-active compounds synthesized by fungi, yeasts, and bacteria. Due to their great metabolic versatility, bacteria are the most traditional and well-known microbial surfactant producers, being Bacillus and Pseudomonas species their typical representatives. To be successfully applied in industry, surfactants need to maintain stability under the harsh environmental conditions present in manufacturing processes; thus, the prospection of biosurfactants derived from extremophiles is a promising strategy to the discovery of novel and useful molecules. Bacterial surfactants show interesting properties suitable for a range of applications in the oil industry, food, agriculture, pharmaceuticals, cosmetics, bioremediation, and more recently, nanotechnology. In addition, they can be synthesized using renewable resources as substrates, contributing to the circular economy and sustainability. The article presents a general and updated review of bacterial-derived biosurfactants, focusing on the potential of some groups that are still underexploited, as well as, recent trends and contributions of these versatile biomolecules to circular bioeconomy and nanotechnology. Graphical Abstract

No abstract

The co-inoculation of Bradyrhizobium with other non-bradyrhizobial strains was already assessed on cowpea, but the co-inoculation of two Bradyrhizobium strains was not tested up to now. This study aimed to evaluate the cowpea growth, N accumulation, and Bradyrhizobium competitiveness of the elite strain B. pachyrhizi BR 3262 when co-inoculated with other efficient Bradyrhizobium from the Brazilian semiarid region. Three potted-plant experiments were carried out. In the first assay, 35 efficient Bradyrhizobium isolates obtained from the semiarid region of Brazil were co-inoculated with the elite strains B. pachyrhizi BR 3262. The experiment was conducted in gnotobiotic conditions. The plant growth, nodulation, N nutritional variables, and nodular occupation were assessed. Under gnotobiotic and non-sterile soil conditions, ten selected bacteria plus the elite strain B. yuanmingense BR 3267 were used at the second and third experiments, respectively. The cowpea was inoculated with the 11 bacteria individually or co-inoculated with BR 3262. The plant growth and N nutritional variables were assessed. A double-layer medium spot method experiment was conducted to evaluate the interaction among the co-inoculated strains in standard and diluted YMA media. The co-inoculation treatments showed the best efficiency when compared to the treatments inoculated solely with BR 3262. This strain occupied a low amount of cowpea nodules ranging from 5 to 67.5%. The treatments with lower BR 3262 nodule occupancy showed the best results for the shoot nitrogen accumulation. The culture experiment showed that four bacteria inhibited the growth of BR 3262. In contrast, seven strains from the soils of Brazilian semiarid region were benefited by the previous inoculation of this strain. In the second and third experiments, the results indicated that all 11 co-inoculated treatments were more efficient than the single inoculation, proofing the best performance of the dual inoculation of Bradyrhizobium on cowpea.

Introdução: Biossurfactantes (BS) são compostos anfifílicos de origem microbiana que apresentam uma ampla diversidade estrutural, consistindo em subprodutos metabólicos de bactérias, fungos e leveduras. A busca por microrganismos produtores de biocompostos de interesse econômico, entre eles os biossurfactantes, tem impulsionado a biotecnologia nas últimas décadas. A medida de tensão superficial (TS) é uma técnica quantitativa largamente empregada no monitoramento da produção de biossurfactantes. Objetivo: Este trabalho teve por objetivo avaliar a produção de BS por duas linhagens de rizóbios (J96) e (16186) pertencentes ao gênero Paraburkholderia diazotrophica, utilizando nove fontes de carbono diferentes. Material e métodos: As bactérias foram cultivadas em meio contendo: NH4Cl (4,0 g/L); NaCl (0,5 g/L); KH2PO4 (0,5 g/L); Na2HPO4 (1,0 g/L); MgSO4.7 H2O (0,5 g/L), acrescido de 10,0 g/L das seguintes fontes de carbono: glicose, óleo de girassol, azeite de oliva, glicerina, lactose, vaselina, óleo de soja, sacarose e óleo de motor. O ensaio foi conduzido a 28ºC e 160 rpm, durante 10 dias em incubadora tipo shaker. Após a separação da biomassa (10.000 g/ 20 min. 4°), o sobrenadante, livres de células, foi utilizado para medida da tensão superficial pelo método do anel de Du Noüy. Resultados: o óleo de girassol foi a melhor fonte de carbono para ambas as linhagens, sendo o valor da TS do meio reduzida de 69,9 mN/m para 28,4 mN/m, para alinhagem J96 e 35,9 mN/m para a linhagem 16186. Conclusão: Os resultados obtidos nesse estudo apontam o potencial biotecnológico dessas bactérias para produção de biossurfactantes quando cultivadas em meio mineral suplementado com óleo de girassol como única fonte de carbono e sob condições específicas de crescimento. Estudos complementares se fazem necessários afim de investigar a natureza química e propriedades dos BS sintetizados pelas linhagens diazotroficas.