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Growth rate and limiting substrate define the nutritional composition and cell size of microbial biomass for food applications

ABSTRACT: Microbial biomass has emerged as a promising sustainable protein alternative. The cultivation conditions affect the composition of microbial cells, and hence their quality and nutritional value. Here, we investigated the relationship between growth rate, substrate availability and cell composition and size of Cupriavidus necator and Komagataella phaffii. Biomass with decreased nucleic acid and increased protein content was produced at low growth rates. Conversely, high rates resulted in larger cells, which could enable more efficient biomass harvesting. The proteome allocation varied across the different growth rates, with more ribosomal proteins at higher rates. Considering the distinct amino acid profiles established for the different cellular components, variations in their abundance impacts the product quality leading to higher cysteine and phenylalanine content at low growth rates. In summary, we demonstrate tradeoffs between nutritional quality and production rate, and we discuss that techno-functional food properties should be considered when designing microbial biomass production processes.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Cupriavidus Necator Komagataella Phaffii

SUBMITTER: Robbin Bouwmeester

LAB HEAD: Korneel Rabaey

PROVIDER: PXD041491 | Pride | 2024-01-26

REPOSITORIES: Pride

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The nutritional composition and cell size of microbial biomass for food applications are defined by the growth conditions.

Sakarika Myrsini M Kerckhof Frederiek-Maarten FM Van Peteghem Lotte L Pereira Alexandra A Van Den Bossche Tim T Bouwmeester Robbin R Gabriels Ralf R Van Haver Delphi D Ulčar Barbara B Martens Lennart L Impens Francis F Boon Nico N Ganigué Ramon R Rabaey Korneel K

Microbial cell factories 20231211 1

<h4>Background</h4>It is increasingly recognized that conventional food production systems are not able to meet the globally increasing protein needs, resulting in overexploitation and depletion of resources, and environmental degradation. In this context, microbial biomass has emerged as a promising sustainable protein alternative. Nevertheless, often no consideration is given on the fact that the cultivation conditions affect the composition of microbial cells, and hence their quality and nutr ...[more]

PMID: 38072930

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Project description:Saccharomyces cerevisiae is an established microbial host for the production of non-native compounds. The synthesis of these compounds typically demands energy and competes with growth for carbon and energy substrate. Uncoupling product formation form growth would benefit product yields and decrease formation of by-product biomass. Studying non-growing metabolically-active yeast cultures provides a first step towards developing S. cerevisiae as a non-growing, robust cell factory. Non-growing metabolically-active cultures can be obtained in retentostat, a glucose-limited, continuous bioreactor system in which biomass accumulates while spent medium is constantly removed. Hitherto retentostat cultures of S. cerevisiae have only been reported under anaerobiosis, condition inappropriate for the production of energy-demanding products. The present study, using retentostat cultures, explores the physiology of non-dividing, fully respiring S. cerevisiae, focusing on industrially-relevant features. Following model-aided experimental design, retentostat cultivations were optimized for accelerated but smooth transition of S. cerevisiae from exponential growth to near-zero growth rates. During 20 days in retentostat the biomass concentration increased, leading very slow growth rates (specific growth rates below 0.001 h-1) but high culture viability (over 80% of viable cells). The maintenance requirement (mATP) was estimated at 0.64 mmolATP.gX-1.h-1, which is remarkably ca. 35% lower than the mATP measured in anaerobic retentostat cultures. Transcriptional down-regulation of genes involved in biosynthesis and up-regulation of stress-responsive genes towards near-zero growth rates corresponded well with data from anaerobic retentostats. More striking was the extreme heat-shock tolerance of S. cerevisiae, which exceeded by far previously reported heat shock tolerance of notoriously robust yeast cultures such as stationary phase cultures. Furthermore, while the metabolic fluxes in the retentostats were relatively low as a result of extreme caloric restriction, off-line measurements revealed that S. cerevisiae retained a high catabolic capacity. The high viability and extreme heat-shock tolerance revealed the robustness of S. cerevisiae at near-zero growth in retentostat. In addition, the relatively low maintenance requirements and high metabolic capacity under severe calorie restriction underline the potential of S. cerevisiae as a non-dividing microbial cell factory for the production of energy-intensive compounds. The retentostat is a promising tool to identify the molecular basis of this extreme robustness. The goal of the present study is to investigate the physiology of aerobic fully respiring S. cerevsiae at near-zero growth rates. Fundamental but industrially-relevant questions were addressed thanks to the design, implementation and study of aerobic retentostat cultivations enabling a rapid but smooth transition of S. cerevisiae from exponential growth to near-zero growth rates.

Project description:Background Lactococcus lactis is recognised as a safe (GRAS) microorganism and has hence gained interest in numerous biotechnological approaches. As it is fastidious for several amino acids, optimization of processes which involve this organism requires a thorough understanding of its metabolic regulations during multisubstrate growth. Results Using glucose limited continuous cultivations, specific growth rate dependent metabolism of L. Lactis including utilization of amino acids was studied based on extracellular metabolome, global transcriptome and proteome analysis. A new growth medium was designed with reduced amino acid concentrations to increase precision of measurements of consumption of amino acids. Consumption patterns were calculated for all 20 amino acids and measured carbon balance showed good fit of the data at all growth rates studied. It was observed that metabolism of L. lactis became more efficient with rising specific growth rate in the range 0.10 – 0.60 h-1, indicated by 30% increase in biomass yield based on glucose consumption, 50% increase in efficiency of nitrogen use for biomass synthesis, and 40% reduction in energy spilling. The latter was realized by decrease in the overall product formation and higher efficiency of incorporation of amino acids into biomass. L. lactis global transcriptome and proteome profiles showed good correlation supporting the general idea of transcription level control of bacterial metabolism, but the data indicated that substrate transport systems together with lower part of glycolysis in L. lactis were presumably under allosteric control. Conclusions The current study demonstrates advantages of the usage of strictly controlled continuous cultivation methods combined with multi-omics approach for quantitative understanding of amino acid and energy metabolism of Lactococcus lactis which is a valuable new knowledge for development of balanced growth media, gene manipulations for desired product formation etc. Moreover, collected dataset is an excellent input for developing metabolic models. For microarray analysis, steady state chemostat culture of L. lactis IL1403 was used as reference (? = 0.10 1/h). Subsequent quasi steady state points from A-stat experiment at specific growth rates 0.52 ± 0.03; 0.42 ± 0.02; 0.29 ± 0.01 1/h in biological duplicates and 0.17 1/h were compared to the reference sample.

Dataset Information

Growth rate and limiting substrate define the nutritional composition and cell size of microbial biomass for food applications

Publications

The nutritional composition and cell size of microbial biomass for food applications are defined by the growth conditions.

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