Abstract A Plackett–Burman Factorial Design of 16 experiments was conducted to assess the influence of nine factors on the production of lipases by filamentous fungi. The factors investigated were bran type (used as the main carbon source), nitrogen source, nitrogen source concentration, inducer, inducer concentration, fungal strain (Aspergillus niger or Aspergillus flavus were selected as good lipase producers via submerged fermentation), pH and agitation. The concentration of the yeast extract and soybean oil and the pH had a significant effect (p < 0.05) on lipase production and were consecutively studied through a Full Factorial Design 23, with the concentration of yeast extract and pH being significant (p < 0.05). These variables were optimized using a central composite design, obtaining maximum lipolytic activities with the use of 45 g/L of yeast extract and pH 7.15. The statistical model showed a 94.12% correlation with the experimental data.

Resumo: O objetivo deste trabalho foi avaliar o efeito das condições de processamento do tempeh de soja sobre o conteúdo de isoflavonas β-glicosídeos e sobre sua bioconversão em agliconas. Diferentes tempos de maceração (6, 12 e 18 horas), cozimento (15, 30 e 45 minutos) e fermentação (18, 24 e 30 horas) com Rhizopus oligosporus a 37°C foram avaliados na preparação do tempeh. Foram utilizados grãos da cultivar 'BRS 267', e o experimento foi realizado de acordo com um delineamento composto central (23). As funções-respostas compreenderam o teor de genistina, malonildaidzina, malonilgenistina, daidzeína e genisteína, quantificadas por cromatografia líquida de ultraeficiência (CLUE). Os tempos de maceração, cozimento e fermentação alteraram o conteúdo, o perfil e a distribuição das diferentes formas de isoflavonas no tempeh. A maior bioconversão de β-glicosídeos em agliconas ocorreu em grãos de soja macerados por 6 horas, cujos cotilédones foram cozidos por 15 minutos e submetidos à fermentação por 18 horas.

Abstract: The objective of this work was to evaluate the effect of the processing conditions of soybean tempeh on the contents of β-glycoside isoflavones and on their bioconversion into aglycones. Different times of soaking (6, 12, and 18 hours), cooking (15, 30, and 45 minutes), and fermentation (18, 24, and 30 hours) with Rhizopus oligosporus at 37°C were evaluated for tempeh preparation. Grains from the cultivar 'BRS 267' were used, and the experiment was carried out according to a central composite design (23). The response functions comprised the contents of genistin, malonyldaidzin, malonylgenistin, daidzein, and genistein, quantified by ultraperformance liquid chromatography (UPLC). Soaking, cooking, and fermentation times change the content, profile, and distribution of the different forms of isoflavones in tempeh. The highest bioconversion of glycoside isoflavones into aglycones occurred in 6-hour soaked soybean grains, whose cotyledons were cooked for 15 minutes and subjected to 18-hour fermentation.