Modelling of DHA Production from S. Limacinum ouc88: fed-batch perspectives

Biotechnology and its need to improve industrial processes have shown the need for techniques that allow processes optimization. Computer simulation offers the advantage of determining production prospects without significant resources and experimentation time. That is why a kinetic study of DHA (docosahexaenoic acid) production from Schizochytrium limacinum OUC88 was developed in this investigation. Based on the above, a mathematical approach to simulate DHA production in a fed-batch model is proposed in this work, using Matlab software. The experimental data for determining kinetic parameters were taken from previous investigations, and a simulated DHA level in the fed-batch mode of 150 g/L was reached. On the contrary, the simulated results in batch mode present only a maximum value of 30 g/L, demonstrating the effectiveness of the fed-batch implementation with perspectives on improving processes.

Composição química e perfil de ácidos graxos no leite orgânico de vacas leiteiras alimentadas com microalgas (Schizochytrium limacinum)

Nosso objetivo foi determinar se a suplementação de microalgas (Schizochytrium limacinum) afeta a produção diária, composição e perfil de ácidos graxos do leite orgânico. Oito vacas em lactação foram mantidas a pasto e divididas em dois grupos: as alimentadas com sabugo de milho como suplemento duas vezes ao dia durante a ordenha (CTL) e as alimentadas com sabugo de milho misturado com 100 g de microalgas (ALG) por vaca diariamente. As microalgas não afetaram a produção e composição diária do leite, mas foi observada uma tendência de redução da gordura do leite. O nível de ácido esteárico no leite de vacas alimentadas com ALG foi significativamente reduzido em 2,46 vezes, enquanto os níveis de ácido elaídico e ácido linoléico conjugado foram significativamente elevados em 3,3 vezes e 1,8 vezes, respectivamente. Uma proporção significativamente maior de PUFA: MUFA foi observada no tratamento com ALG, enquanto a proporção de MUFA: ácido graxo saturado mostrou uma tendência a aumentar (P = 0,073). Microalgas ricas em ácidos graxos ômega-3 enriquecem com sucesso o leite orgânico sem afetar negativamente a produtividade ou composição. Os consumidores podem ser atraídos para aumentar a ingestão de gordura polinsaturada ômega 3 do leite orgânico. Esses resultados podem apoiar a decisão de nutricionistas e agricultores de alimentar o gado leiteiro com microalgas, uma vez que é economicamente viável.

Function of ORFC of the polyketide synthase gene cluster on fatty acid accumulation in Schizochytrium limacinum SR21

Background As a potential source of polyunsaturated fatty acids (PUFA), Schizochytrium sp. has been widely used in industry for PUFA production. Polyketide synthase (PKS) cluster is supposed to be the primary way of PUFA synthesis in Schizochytrium sp. As one of three open reading frames (ORF) in the PKS cluster, ORFC plays an essential role in fatty acid biosynthesis. However, the function of domains in ORFC in the fatty acid synthesis of Schizochytrium sp. remained unclear. Results In this study, heterologous expression and overexpression were carried out to study the role of ORFC and its domains in fatty acid accumulation. Firstly, ORFC was heterologously expressed in yeast which increased the PUFA content significantly. Then, the dehydratase (DH) and enoyl reductase (ER) domains located on ORFC were overexpressed in Schizochytrium limacinum SR21, respectively. Fatty acids profile analysis showed that the contents of PUFA and saturated fatty acid were increased in the DH and ER overexpression strains, respectively. This indicated that the DH and ER domains played distinct roles in lipid accumulation. Metabolic and transcriptomic analysis revealed that the pentose phosphate pathway and triacylglycerol biosynthesis were enhanced, while the tricarboxylic acid cycle and fatty acids oxidation were weakened in DH-overexpression strain. However, the opposite effect was found in the ER-overexpression strain. Conclusion Therefore, ORFC was required for the biosynthesis of fatty acid. The DH domain played a crucial role in PUFA synthesis, whereas the ER domain might be related to saturated fatty acids (SFA) synthesis in Schizochytrium limacinum SR21. This research explored the role of ORFC in the PKS gene cluster in Schizochytrium limacinum and provided potential genetic modification strategies for improving lipid production and regulating PUFA and SFA content.

Occurrence of Antibiotic Resistance Genes in Hermetia illucens Larvae Fed Coffee Silverskin Enriched with Schizochytrium limacinum or Isochrysis galbana Microalgae

Hermetia illucens larvae are among the most promising insects for use as food or feed ingredients due to their ability to convert organic waste into biomass with high-quality proteins. In this novel food or feed source, the absence of antibiotic-resistant bacteria and their antibiotic resistance (AR) genes, which could be horizontally transferred to animal or human pathogens through the food chain, must be guaranteed. This study was conducted to enhance the extremely scarce knowledge on the occurrence of AR genes conferring resistance to the main classes of antibiotics in a rearing chain of H. illucens larvae and how they were affected by rearing substrates based on coffee silverskin supplemented with increasing percentages of Schizochytrium limacinum or Isochrysis galbana microalgae. Overall, the PCR and nested PCR assays showed a high prevalence of tetracycline resistance genes. No significant effect of rearing substrates on the distribution of the AR genes in the H. illucens larvae was observed. In contrast, the frass samples were characterized by a significant accumulation of AR genes, and this phenomenon was particularly evident for the samples collected after rearing H. illucens larvae on substrates supplemented with high percentages (>20%) of I. galbana. The latter finding indicates potential safety concerns in reusing frass in agriculture.