The wide application of beneficial microorganisms in agriculture as inoculants to combat pests and diseases and/or to improve soil fertility and the nutrients availability for plants has been considered as an effective and more sustainable alternative than chemical fertilizers and agricultural defensives. However, it is necessary to examine all processing steps of these bio-based products under a more integrated view including the type of microorganisms and the whole production process in order to reduce dependence on synthetic chemical inputs. Here, recent developments on the production and formulation technologies of microbial inoculants and the main types of inoculants currently applied in agriculture are addressed. The different types of microbial formulations are compared with emphasis on the encapsulation technology. Moreover, the application of biofertilizers in seed coating and a new approach to apply biocomposites as fertilizers are discussed, presenting the main challenges and future perspectives to promote more sustainable agriculture practices.

Resumo: O objetivo deste trabalho foi avaliar a solubilização de fósforo de rocha fosfática por Aspergillus niger, em cultivo em estado sólido (CES) em bagaço de cana-de-açúcar (Saccharum officinarum), por meio da maximização da eficiência de produção de ácido cítrico. A rocha fosfática (IPR) escolhida para o estudo é um tipo de rocha ígnea com solubilização de fósforo muito baixa, obtida da empresa Itafós, em Arraias, no estado do Tocantins. Utilizou-se o delineamento composto central rotacional (DCCR) como ferramenta estatística para avaliar o efeito das concentrações da fonte de carbono (sacarose) e da IPR no meio para CES como estratégia para melhorar a solubilização de P. Para o processo sem a IPR, houve produção de ácido cítrico de até 300 g por quilograma de substrato. Os experimentos em DCCR mostraram que a adição da IPR afetou a produção de ácido cítrico, com valores de P solubilizado de 1,44 a 2,72 g por quilograma de substrato e rendimento de P solubilizado de 12,96 a 48,94%. Além disso, a análise da razão P solubilizado/sacarose mostrou condições favoráveis para solubilização de P e produção de ácido cítrico. Os valores de P solubilizado são promissores, ao se considerar que a IPR apresenta baixa solubilização, com apenas 8,6% de P2O5. No geral, esses resultados podem contribuir para o desenvolvimento de processos biotecnológicos, para a produção de fertilizantes fosfatados ambientalmente favoráveis, como alternativa para uma agricultura mais sustentável.

Abstract: The objective of this work was to evaluate the solubilization of phosphorus from a phosphate rock by Aspergillus niger, under solid-state cultivation (SSC) in sugarcane (Saccharum officinarum) bagasse, by maximizing the efficiency of citric acid production. The phosphate rock (IPR) chosen for the study is a type of igneous rock with a very low phosphorus solubility, obtained from the Itafós company, in Arraias, in the state of Tocantins, Brazil. The rotatable central composite design (RCCD) was used as a statistical tool to evaluate the effect of the concentrations of the carbon source (sucrose) and of the IPR on the SSC medium as a strategy to improve P solubilization. In the process without the IPR, there was a citric acid production of up to 300 g per kilogram of substrate. The experiments in the RCCD showed that the addition of the IPR affected citric acid production, with values of solubilized P ranging from 1.44 to 2.72 g per kilogram of substrate and of solubilized P yield from 12.96 to 48.94%. The analysis of the solubilized P/sucrose ratio showed favorable conditions for P solubilization and citric acid production. The obtained solubilized P values are promising considering that the IPR has a very low solubilization, with only 8.6% P2O5. Overall, these findings could contribute to the development of biotechnological processes for producing eco-friendly phosphate fertilizers, as an alternative for a more sustainable agriculture.

The second generation (2G) ethanol obtained from lignocellulosic biomass has been considered as a potential alternative source of energy for the transportation sector. However, the technologies to convert lignocellulose into fermentable sugars still face several challenges. One of the major challenges of this process is related to the cost of the cellulolytic enzymes. Thus, the development of bioprocesses for enzyme production and strategies to increase the final yield of the enzymatic hydrolysis reactions are required to ensure the economic feasibility of the biomass conversion process. In this review, it is discussed the progress related to fungal enzyme technology over the past few years with major emphasis on the biocatalysts needed for cellulose degradation as well as on cultivation strategies for the production of enzymes on-site. The potential of applying secretome analysis as a tool for the characterization of the enzymatic complexes and some limitations on the use of enzymatic cocktails in the saccharification step, such as the unproductive adsorption of enzymes onto lignin are also discussed in light of the recent literature.