Novel microalgae formulations comprising lactic acid bacteria for human consumption

• Autor(a) principal: Ribeiro, Mónica Costa
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.14/33314
• topic: Chlorella vulgaris; Lactic acid bacteria; Probiotic; Vitamin B12; Bactérias do ácido lático; Probiótico; Vitamina B12; Domínio/Área Científica::Ciências Naturais::Ciências Biológicas

Hypocobalaminemia is a global health condition that has several health implications. Bacteria can synthetise de novo vitamin B12 whilst humans acquire it from dietary sources. To reverse vitamin B12 deficiency, microbiological alternatives have been developed to increase vitamin B12 content in food and research has focused on lactic acid bacteria (LAB) as potential cobalamin producers. Chlorella vulgaris is one of the most relevant eukaryotic green microalgae, taking a significant role in human nutrition. It was already reported that C. vulgaris can uptake exogenous cobalamin from the environment, thus being capable of being used as fortified food. In the present work, selected strains of LAB, isolated from a C. vulgaris culture grown in a photobioreactor, were assessed for their cobalamin biosynthesis capacity. Pediococcus pentosaceus L51 presented the highest cobalamin production capacity (28.19 ± 2.27 pg mL¬1 ), followed by Lactococcus lactis E32 and Lactobacillus brevis G31 which produced, respectively, 6.18 ± 1.08 pg mL¬1 and 5.47 ± 0.37 pg mL¬1 . Lactobacillus plantarum G12 was not considered a cobalamin producer. Genes involved in cobalamin biosynthetic pathway were searched through comparative genomics. Four genes (hemL, cbiT, cobD and cobC) were identified in Lac. lactis E32, L. brevis G31 and L. plantarum G12 genome. Although hemL was not present in P. pentosaceus L51 genome, gene cobA was identified. Moreover, in this strain two genes associated with cobalamin¬dependent propanediol utilization (pduU and pduV) were also identified. Strains selected as potential cobalamin producers were lyophilized along with C. vulgaris culture. Addition of P. pentosaceus L51 grown in organic medium N formulation to C. vulgaris culture successfully increased vitamin B12 content in the mixed culture freeze¬dried powder to a value of 522.97 ± 23.09 ng g¬1 . Additionally, a vitamin B12 content of 10.22 ± 0.53 ng g¬1 in a freeze¬dried powder of C. vulgaris culture grown axenically in vitamin B12-free medium was determined. LAB survival during freeze and freeze-dried storage was studied. During frozen storage, C. vulgaris demonstrated a protective effect on the viability of LAB strains. However, the opposite effect was verified during storage of freeze¬dried cultures. In both conditions, P. pentosaceus L51 has shown evidences to be more resistant than Lac. lactis E32 and L. brevis G31 to stress conditions.