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Qymyz is a traditional acidic and ethanolic beverage in central Asian countries made from mare milk fermentation with lactic acid bacteria (LAB) and yeasts. Modeling the growth of microorganisms during fermentation is one of the methods used to control the quality of fermented products. The objective of the study was, firstly, to model the growth kinetics of Kazachstania unispora found in qymyz, and, secondly, to understand their interaction with Lacticaseibacillus casei and Lactobacillus kefiri during the fermentation of mare milk. The K. unispora optimum values of pH and temperature were 4.81 ± 0.22 and 30.16 ± 0.53 °C, respectively, with an optimal growth rate (µopt) of 0.56 ± 0.02 h−1. K. unispora had an ethanol production rate of 6.1 × 10−8 mg·CFU−1. Growth, in terms of limiting substrates showed a lower Ks value for galactose at 0.13 ± 0.04 mg·mL−1 with µopt of 0.45 ± 0.01 h−1, while, for glucose, the Ks was 0.24 ± 0.03 mg·mL−1 with the same µopt. Cocultures of K. unispora were conducted with L. casei and L. kefiri in a synthetic medium and mare milk. The results showed that K. unispora growth was limited and, thus, its ethanol production capacity was inhibited. VOC analysis of mare milk fermented with the studied strains and their cocultures resulted in 37 major volatile compounds. Statistical analysis of the VOC profiles showed that K. unispora modulates the aroma production in coculture with LAB.

The growth characteristics of two strains of lactic acid bacteria (LAB), Lacticaseibacillus casei and Lactobacillus kefiri, isolated from qymyz, a traditional fermented mare milk beverage, were studied and modeled, including the effect of different carbohydrates, pH, and temperature. Along with population, substrates, and metabolites, lactic acid and ethanol were monitored by HPLC. Growth parameters were obtained from mono- and biphasic logistic growth models that fit the population evolution of L. casei and L. kefiri, respectively. The effect of temperature and pH on the growth rate was represented with the gamma concept model, while the effect of the limiting substrate was evaluated according to the Monod equation. Lastly, a simplified Luedeking and Piret equation was used to represent metabolite production. The optimum values of pH and temperature were 6.69 ± 0.20, 38.63 ± 0.32 °C, 5.93 ± 0.08, and 33.15 ± 0.53 °C, with growth rate values of 0.66 ± 0.01 h−1 and 0.29 ± 0.01 h−1 for L. casei and L. kefiri, respectively. L. casei had a homofermentative pathway, while L. kefiri was heterofermentative, with an ethanol production rate of 2.90 × 10−9 mg·CFU−1. The Monod model showed that L. casei had the lowest Ks value for lactose, while for L. kefiri, it was the highest among milk carbohydrates. These results show that the population of the two LAB strains and therefore the concentrations of acid and ethanol can be controlled by the fermentation conditions and that our model can help to significantly improve the production of qymyz.

The effect of Akpan (yoghurt-like product) consumption on the human intestinal microbiota was examined. The prebiotic potential of Akpan was assessed by in vitro fermentation using, as inocula, individual probiotic strains and faecal samples from three healthy donors. In this latter case, the prebiotic activity was assessed through the quantification of short chain fatty acid (SCFA) production, the evolution of the pH and the evaluation of dynamic bacterial population by fluorescent in situ hybridization (FISH). Results demonstrated that Akpan was metabolized after 44 h of fermentation, exerting a prebiotic effect, similar to that observed for fructooligosaccharides (FOS). All the considered bacterial groups significantly increased after Akpan and FOS fermentation. Under the tested conditions, no significant differences between the SCFA concentration produced by Akpan and FOS after of incubation were detected. Our findings contribute to support the utilization of Akpan as a functional food with potential beneficial effects on gastrointestinal health.

Sequências do DNA de uma região em comum de múltiplos indiví­duos de uma população podem revelar polimorfismos que permitem o estudo da evolução do genoma e suas histórias de seleções, migrações e recombinações. Adicionando-se a esses polimorfismos da população informações quanto origem geográfica, viabiliza-se um estudo filogeográfico que permite a elaboração de cenários de evolução após a domesticação; bem como quais eventos (mutações ou recombinações) mais influenciaram a diversidade genética (DG) desta população, para aquela região do DNA em estudo. Por outro lado, a associação desses polimorfismos das sequências com as caracterí­sticas de interesse estabelece um estudo de associação. Neste contexto, este trabalho visou mostrar a aplicação do polimorfismo de sequências de DNA em um estudo de filogeografia e de associação. Para ambos os estudos foram utilizados dezenove segmentos de seis genes candidatos (Sh2, Bt2, Sssl, Ael, Wx e 02) em uma coleção de sorgo (Sorghum bicolor L. Moench), composta por 210 acessos. Os genes Sh2, Bt2, Sssl, Ael e Wx estão envolvidos na sí­ntese do amido e o gene 02 na sí­ntese de proteí­nas de reserva. A DG foi menor nos genes Sh2, Bt2 e Sssl; e maior para Ael, Wx e 02. Os testes estatí­sticos revelaram um elevado número de associações falso-positivas em função da estruturação da coleção, porém foram mantidas várias associações corroboradas pela co-localização com QTLs de sorgo e de milho.

A global model of the lactic fermentation step of gowé was developed by assembling blocks hosting models for bacterial growth, lactic acid production, and the drop of pH during fermentation. Commercial strains of Lactobacillus brevis and of Lactobacillus plantarum were used; their growth was modeled using Rosso’s primary model and the gamma concept as a secondary model. The optimum values of pH and temperature were 8.3 ± 0.3, 44.6 ± 1.2 °C and 8.3 ± 0.3, 3.2 ± 37.1 °C with μmax values of 1.8 ± 0.2 and 1.4 ± 0.1 for L. brevis and L. plantarum respectively. The minimum inhibitory concentration of undissociated lactic acid was 23.7 mM and 35.6 mM for L. brevis and L. plantarum, respectively. The yield of lactic acid was five times higher for L. plantarum than for L. brevis, with a yield of glucose conversion to lactic acid close to 2.0 for the former and 0.8 for the latter. A model was developed to predict the pH drop during gowé fermentation. The global model was partially validated during manufacturing of gowé. The global model could be a tool to aid in the choice of suitable starters and to determine the conditions for the use of the starter.

Abstract: Age of plant and environmental conditions during growing may affect texture (friability) and taste of boiled cassava roots. We investigated the quality of boiled roots of seven cultivars harvested at 10, 12 and 14months in three different seasons. Sensory taste (sweet or bitter) of boiled cassava root could not be correlated with sugar content and/or cyanide potential, which both interfere with taste perception; hence, bitterness is not a good indicator of the poisonous character of cassava roots. Improved cultivars generally showed lower friability scores, independently of plant age (10–14months) or season. Rainfall before harvest directly lowers dry matter and mealiness of boiled roots. Cultivar and rainfall effects are discussed in relation to pectins (higher content for improved cultivars) that are suspected to be the major biochemical cause of vegetable mealiness. [ABSTRACT FROM AUTHOR]