-The kinetic analysis of Bacillus thuringiensis var. israelensis (Bti) growth is often hindered by the impossibility of using conventional methods to measure biomass concentration in natural raw-material-based media, which normally have a high content of insoluble solids. In this work, application of a mathematical model based on respiratory parameters in the estimation of Bti biomass concentration was evaluated. The values obtained for the respiratory parameters true cell yield from oxygen consumption and maintenance coefficient for oxygen (m O ) were 0.091 g cell/mmol O 2 and 2.1 mmol O 2 /g cell/hour, respectively. With these constants and the oxygen uptake rates obtained from oxygen balance calculations, cell concentrations of Bti were estimated in batch runs with initial glucose concentrations from 10 to 80 g/L and were found to be in good agreement with experimental data.

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, VINICIUS OLIVEIRA CARLESSO 4 , MÁRCIA TEREZINHA RAMOS OLIVEIRA 5 RESUMO -O desenvolvimento de modelos matemáticos que correlacionem a permissividade elétrica relativa ε' e o fator de perda dielétrica ε" à quantidade de água presente em amostras de sementes é um passo fundamental no desenvolvimento de medidores em linha do teor de água que possam ser empregados no controle automático de processos como colheita, secagem e aeração. Esse trabalho consistiu na avaliação de três modelos dielétricos para determinação do teor de água de sementes de café, sem a influência do fluxo de massa. Foram utilizadas amostras das variedades Catuaí Amarelo, Catuaí Vermelho e Mundo Novo, com teores de água entre 11 e 23% b.u. e massa específica aparente no intervalo 326 kg m -3 < ρ < 455 kg m -3. Dos modelos obtidos, apenas aquele que utiliza a medição simultânea de ε' e ε", a 0,5 e 5,0 MHz, permite estimar o teor de água de sementes de café com o grau de acurácia desejado. Os erros padrão de calibração e predição foram de 1,3 e 1,2 pontos percentuais, respectivamente.Termos para indexação: Coffea arabica, umidade, propriedades dielétricas, instrumentação. MOISTURE DETERMINATION IN COFFEE SEEDS BY THE CAPACITANCE METHOD AT RADIOFREQUENCIESABSTRACT -The development of mathematical models capable of relating the relative permittivity ε' and the loss factor ε" of seeds to their moisture content is a fundamental step towards designing seed moisture meters for on-line operations in automatic control processes such as seed harvest, drying and aeration. The object of this research is the assessment of three dielectric models that would allow the density-independent determination of the moisture content of moving seeds of parchment coffee. Seed samples of varieties Catuaí Amarelo, Catuaí Vermelho and Mundo Novo with moisture contents in the range from 11 to 23% w.b., and bulk density ranging from 326 to 455 kg.m -3 have been used. In terms of instrumentation accuracy the best bulk-density dielectric model for coffee seeds moisture content estimation was the one which employed both ε' and ε" measured at 0.5 and 5.0 MHz as indicators of the amount of water present in the seed samples. The standard errors of calibration and prediction were 1.3 and 1.2 percentage points moisture, respectively