Insights Into the Complexity of Yeast Extract Peptides and Their Utilization by Streptococcus thermophilus

Streptococcus thermophilus, an extensively used lactic starter, is generally produced in yeast extract-based media containing a complex mixture of peptides whose exact composition remains elusive. In this work, we aimed at investigating the peptide content of a commercial yeast extract (YE) and identifying dynamics of peptide utilization during the growth of the industrial S. thermophilus N4L strain, cultivated in 1 l bioreactors under pH-regulation. To reach that goal, we set up a complete analytical workflow based on mass spectrometry (peptidomics). About 4,600 different oligopeptides ranging from 6 to more than 30 amino acids in length were identified during the time-course of the experiment. Due to the low spectral abundance of individual peptides, we performed a clustering approach to decipher the rules of peptide utilization during fermentation. The physicochemical characteristics of consumed peptides perfectly matched the known affinities of the oligopeptide transport system of S. thermophilus. Moreover, by analyzing such a large number of peptides, we were able to establish that peptide net charge is the major factor for oligopeptide transport in S. thermophilus N4L

Influência de diferentes extratos de levedura (insumos) no crescimento celular de Xanthomonas arboricola pv pruni cepa 101/ Influence of different yeast extracts (inputs) on the cell growth of Xanthomonas arboricola pv pruni strain 101

Xantana é um heteropolissacarídeo produzido por bactérias do gênero Xanthomonas. Esse biopolímero desempenha diversas funções de grande importância para indústrias de variados setores. O processo de produção de xantana é realizado em duas etapas: crescimento celular e produção do biopolímero, e ambas são importantes para a obtenção de xantana com rendimento e qualidade satisfatórios, os quais são influenciados por diferentes fatores, dentre eles os meios de cultivo utilizados. Objetivou-se avaliar o crescimento bacteriano de Xanthomonas arboricola pv pruni cepa 101 em meio de cultivo complexo YM adicionado de diferentes extratos de levedura, sendo um tradicional - controle (1) - e outros alternativos de menor custo - 560PW (2), 810PW (3), 845MG (4), 851MG (5), 861PW (6) - e relacionar com o teor de nitrogênio fornecido. Avaliou-se o crescimento celular (UFC.mL-1) e o teor de nitrogênio (mg.dL-1) nos tempos 24 h e em 0 e 24 h de crescimento celular, respectivamente. Não observou-se diferença estatística entre a concentração celular final obtida com extrato controle e os extratos alternativos. A concentração celular final variou entre 3,1 × 1010 a 5,2 × 1010 UFC.mL-1. O uso dos extratos de levedura 4, 6 e o controle resultaram em maior disponibilidade de nitrogênio no meio de cultivo no tempo inicial e ao final, e têm potencial para propiciar um maior crescimento celular. Observou-se aumento no teor de nitrogênio no tempo final, provavelmente devido à hidrólise celular parcial.  O teor inicial de nitrogênio variou de 9,11 a 12,04 e o final de 31,41 a 47,51 mg.dL-1, respectivamente. Os diferentes extratos de levedura avaliados são substitutos adequados para o crescimento celular da bactéria X. arboricola pv pruni cepa 101, e provavelmente para outras cepas da espécie, com resultados equivalentes ao obtido com o extrato controle

Faecalibacterium duncaniae A2‐165 growth is strongly promoted by yeast extract and vitamin B5 in cGMP medium

Abstract Several gut microbial species within the Faecalibacterium genus have emerged as promising next‐generation probiotics (NGP) due to their multifunctional protective effects against gastrointestinal and systemic disorders. To enable clinical studies and further applications, improved methods for cultivating Faecalibacterium must be developed in compliance with current Good Manufacturing Practice regulations, which is complicated by its oxygen sensitivity and complex nutritional requirements. Different yeast‐based nutrients (YBNs), including yeast extracts (YEs) and yeast peptones (YPs), are ubiquitously used when cultivating microbes to supply a broad range of macro‐ and micronutrients. In this study, we evaluated six experimental YBNs, namely three YEs, two YPs and a yeast cell wall product (YCW), and eight B‐vitamins in the cultivation of Faecalibacterium duncaniae A2‐165, former Faecalibacterium prausnitzii, using growth assays in microtitre plates, dose‐effect studies in Hungate tube fermentations and fully controlled bioreactor experiments. We demonstrated that YEs promote F. duncaniae A2‐165 growth in a nutritionally limited medium, while YPs and YCW lacked essential growth factors for enabling cell propagation. High cell density was obtained in controlled bioreactors using a medium containing 2–4% of a selected YE and 1% casein peptone (3.4 ± 1.7 × 109–5.1 ± 1.3 × 109 cells mL−1). Among all tested B‐vitamins, we identified B5 as a strong growth promoter. Replacing casein peptone with YP and supplementing with vitamin B5 further increased biomass by approximately 50% (6.8 ± 1.7 × 109 cells mL−1). Hence, empirical selection of YE, YP and B5 allowed formulation of a high‐yielding animal allergen‐free nutritive medium to produce F. duncaniae A2‐165. Selecting nutritionally suitable YBNs and combining these with other key nutrients are important steps for optimizing production of NGP with high yields and lower cost