Microbial sources of protein

Hydrogen oxidising bacteria for production of single‐cell protein and other food and feed ingredients

Using hydrogen oxidising bacteria to produce protein and other food and feed ingredients is a form of industrial biotechnology that is gaining traction. The technology fixes carbon dioxide into products without the light requirements of agriculture and biotech that rely on primary producers such as plants and algae while promising higher growth rates, drastically less land, fresh water, and mineral requirements. The significant body of scientific knowledge on hydrogen oxidising bacteria continues to grow and genetic engineering tools are well developed for specific species. The scale-up success of other types of gas- fermentation using carbon monoxide or methane has paved the way for scale-up of a process that uses a mix of hydrogen, oxygen, and carbon dioxide to produce bacteria as a food and feed ingredients in a highly sustainable fashion.

Composição centesimal e valor protéico de levedura residual da fermentação etanólica e de seus derivados

Este trabalho teve por objetivo promover a autólise e o fracionamento da levedura (Saccharomyces sp.) para produção de autolisado e extrato, bem como para produção de concentrado protéico fosforilado, a partir da levedura residual das destilarias de álcool etílico. Foram estudados a composição centesimal, o perfil de aminoácidos essenciais e o valor protéico dos três derivados comparativamente à levedura íntegra não processada. Proteína e carboidrato (fibra alimentar) foram os principais componentes da levedura íntegra e do autolisado. No extrato e no concentrado protéico predominaram proteína e minerais (cinzas). O autolisado e a levedura íntegra apresentaram os melhores índices de aminoácidos essenciais, seguidos pelo concentrado protéico e pelo extrato. A digestibilidade da proteína variou de 68% para a levedura íntegra a 91% para o extrato. Os índices de quociente de utilização líquida da proteína variaram de 2,1 para a levedura íntegra a 4,3 para a caseína (referência). Não houve diferença estatística no quociente de utilização líquida da proteína entre o autolisado (4,1), o extrato (3,9) e o concentrado protéico (4,2). O concentrado protéico promoveu o maior crescimento no período (21 dias), seguido do extrato e o autolisado. As células íntegras apresentaram a menor capacidade para promover crescimento em rato.

Determinação do valor protéico de células íntegras, autolisado total e extrato de levedura (Saccharomyces sp.)

Biomassa de células de levedura, limpa e desamargada, bem como seus derivados autolisado total e extrato de levedura, desidratados em spray dryer foram analisados por ensaio biológico com ratos da linhagem Wistar, em crescimento, para determinação do valor nutritivo da proteína e avaliação do impacto da utilização desses produtos, como única fonte de proteína, nos níveis séricos de triacilgliceróis, colesterol total, ácido úrico e de Lipoproteína de Alta Densidade-colesterol. Células íntegras, autolisado total e extrato de levedura não diferiram estatisticamente (p.<= 0,05) quanto aos índices do quociente de eficiência protéica e quociente de eficiência protéica líquida, significativamente inferiores aos da caseína. A capacidade de produzir crescimento foi maior para a caseína, seguida das células íntegras, do extrato e do autolisado total, em ordem decrescente. A utilização líquida da proteína das dietas confirma os resultados de quociente de eficiência protéica e quociente de eficiência protéica líquida, em que os produtos de levedura não diferiram entre si, mas foram inferiores à caseína. No geral, o valor nutritivo da proteína de levedura variou na faixa de 80-85% da caseína. Os níveis séricos de ácido úrico se elevaram nos ratos em dietas de levedura, permanecendo porém na faixa considerada de normalidade. A dieta com autolisado total produziu uma redução na concentração sangüínea de triacilgliceróis, o que não ocorreu nas demais dietas. Para colesterol total e Lipoproteína de Alta Densidade-colesterol, todas as dietas de levedura se comportaram semelhantemente, não diferindo entre si e do controle de caseína.

Studies on protein production by yeasts. III. Effects of different levels of nitrogen and phosphorus

The four strains of yeasts that gave good growth in molasses medium, short generation time, and high protein content were selected for further studies in a trial for increasing their yield and protein content. Therefore, the effect of different levels of ammonium sulphate and potassium dihydrogen phosphate on the growth and protein synthesis of the strains was investigated, using molasses as a source of carbon. The results revealed that the most suitable concentrations of ammonium sulphate in the propagation medium lie between 0.40 to 0.55% for the production of high yield and protein content of strains S. cerevisiae (Gr. 104), C. utilis (F. 86), C. tropicalis (F. 35), and H. anomala (Gr. 5). The optimum concentration of potassium dihydrogen phosphate lies between 0.2 to 0.3% for the same strains. S. cerevisiae (Gr. 104) seemed to be the most efficient strain that gave the best growth, high percentage of protein, and essential amino acids in molasses medium.

Studies on protein production by yeasts. IV. Incremental feeding modulus

S. cerevisiae Gr. 104 which seemed to be the most efficient strain in protein production, was used for investigating its optimum incremental feeding modulus that gives the highest economical yield. Therefore, different hourly rates of incremental feeding, ranging from 1.14 to 1.22, were used and the yeast yield for each rate was determined. Experiments were carried out in a laboratory fermentor vessel of 5 liter capacity, using molasses, ammonium sulphate, and potassium dihydrogen phosphate as feeding substances with optimum pH, temperature, and effective aeration. The optimum incremental feeding for this strain (which is the rate of molasses feeding corresponding to the exponential growth rate) was found to be 1.18. At this rate the best economical use of the substrate was obtained with the production of yield, close to the theoretically calculated yield.

Protein content and amino acid composition of certain fungi evaluated for microbial protein production

The protein and total amino acid contents of four mycelial fungal strains and one yeast were approximately the same for cultures harvested in the mid-log and early stationary growth phases. It was found that Fusarium oxysporum and Fusarium moniliforme contained approximately 30% more protein and total amino acids than Aspergillus niger. The amino acid composition of mycelial protein compares favorably with that of British Petroleum yeast protein Toprina produced commercially on hydrocarbon substrates. Fusarium spp. may be suitable for commercial production of microbial protein, especially when low-cost agricultural or industrial waste products are readily available as energy sources. Genetic manipulation of these fungi, such as induction of mutant strains through irradiation, may be desirable to obtain a mycelial product of improved yield and/or quality.

Enhancement of resistance to infectious diseases by oral administration of brewer's yeast

The effect of oral administration of brewer's yeast on resistance to infectious diseases was studied in laboratory animals. It was shown that there was a significantly increased enhancement of resistance to seasonal respiratory and enteric infections in rhesus monkeys. Similarly, enhanced resistance to experimental chronic infections was observed in mice after yeast administration. A 2-week lag occurred between the initiation of yeast treatment and the expression of enhanced resistance. Study of the mechanism of the yeast-induced enhancement of resistance to infection leads to the conclusion that it is based on in vivo stimulation of phagocytosis, as measured by the "phagocytic index." No effect of brewer's yeast on circulating antibody levels was detected.