The type of microorganism and substrate determines the odor fingerprint of dried bacteria targeting microbial protein production

From anaerobic digestion to single cell protein synthesis: A promising route beyond biogas utilization

The accumulation of a large amount of organic solid waste and the lack of sufficient protein supply worldwide are two major challenges caused by rapid population growth. Anaerobic digestion is the main force of organic waste treatment, and the high-value utilization of its products (biogas and digestate) has been widely concerned. These products can be used as nutrients and energy sources for microorganisms such as microalgae, yeast, methane-oxidizing bacteria(MOB), and hydrogen-oxidizing bacteria(HOB) to produce single cell protein(SCP), which contributes to the achievement of sustainable development goals. This new model of energy conversion can construct a bioeconomic cycle from waste to nutritional products, which treats waste without additional carbon emissions and can harvest high-value biomass. Techno-economic analysis shows that the SCP from biogas and digestate has higher profit than biogas electricity generation, and its production cost is lower than the SCP using special raw materials as the substrate. In this review, the case of SCP-rich microorganisms using anaerobic digestion products for growth was investigated. Some of the challenges faced by the process and the latest developments were analyzed, and their potential economic and environmental value was verified.

Growth Prediction of the Total Bacterial Count in Freshly Squeezed Strawberry Juice during Cold Storage Using Electronic Nose and Electronic Tongue

The growth models of total bacterial count in freshly squeezed strawberry juice were established by gas and taste sensors in this paper. By selecting the optimal sensors and fusing the response values, the Modified Gompertz, Logistic, Huang and Baranyi models were used to predict and simulate the growth of bacteria. The results showed that the R² values for fitting the growth model of total bacterial count of the sensor S7 (an electronic nose sensor), of sweetness and of the principal components scores were 0.890-0.944, 0.861-0.885 and 0.954-0.964, respectively. The correlation coefficients, or R-values, between models fitted by the response values and total bacterial count ranged from 0.815 to 0.999. A single system of electronic nose (E-nose) or electronic tongue (E-tongue) sensors could be used to predict the total bacterial count in freshly squeezed strawberry juice during cold storage, while the higher rate was gained by the combination of these two systems. The fusion of E-nose and E-tongue had the best fitting-precision in predicting the total bacterial count in freshly squeezed strawberry juice during cold storage. This study proved that it was feasible to predict the growth of bacteria in freshly squeezed strawberry juice using E-nose and E-tongue sensors.

Microalgae-bacteria consortium for wastewater treatment and biomass production

The diversity of microalgae and bacteria allows them to form a complementary consortium for efficient wastewater treatment and nutrient recovery. This review highlights the potential of wastewater-derived microalgal biomass as a renewable feedstock for producing animal feed, biofertilisers, biofuel, and many valuable biochemicals. Data corroborated from this review shows that microalgae and bacteria can thrive in many environments. Microalgae are especially effective at utilising nutrients from the water as they grow. This review also consolidates the current understanding of microalgae characteristics and their interactions with bacteria in a consortium system. Recent studies on the performance of only microalgae and microalgae-bacteria wastewater treatment are compared and discussed to establish a research roadmap for practical implementation of the consortium systems for various wastewaters (domestic, industrial, agro-industrial, and landfill leachate wastewater). In comparison to the pure microalgae system, the consortium system has a higher removal efficiency of up to 15% and shorter treatment time. Additionally, this review addresses a variety of possibilities for biomass application after wastewater treatment.

Potential use of microbial engineering in single-cell protein production

Single-cell proteins (SCPs) have been widely used in human food and animal feed applications, still, there are challenges in their production and commercialization. Recently, advances in microbial synthetic biology, genomic engineering, and biofoundry technologies have offered capabilities to effectively and rapidly engineer microorganisms for improving the productivity, nutritional, and functional quality of SCPs. In this review, we discuss various synthetic biology, genomic engineering, and biofoundry tools that can be harnessed for SCP production and genetic modification. We also describe the current and potential applications of genetic modification in producing intermediate feedstocks, as well as biomass-based and multifunctional SCPs. Finally, we discuss the technological and policy-control related challenges encountered when deploying genetic modification in SCP production for animal feed and human food applications.

Unlocking the genomic potential of aerobes and phototrophs for the production of nutritious and palatable microbial food without arable land or fossil fuels

The increasing world population and living standards urgently necessitate the transition towards a sustainable food system. One solution is microbial protein, i.e. using microbial biomass as alternative protein source for human nutrition, particularly based on renewable electron and carbon sources that do not require arable land. Upcoming green electrification and carbon capture initiatives enable this, yielding new routes to H2, CO2 and CO2-derived compounds like methane, methanol, formic- and acetic acid. Aerobic hydrogenotrophs, methylotrophs, acetotrophs and microalgae are the usual suspects for nutritious and palatable biomass production on these compounds. Interestingly, these compounds are largely un(der)explored for purple non-sulfur bacteria, even though these microbes may be suitable for growing aerobically and phototrophically on these substrates. Currently, selecting the best strains, metabolisms and cultivation conditions for nutritious and palatable microbial food mainly starts from empirical growth experiments, and mostly does not stretch beyond bulk protein. We propose a more target-driven and efficient approach starting from the genome-embedded potential to tuning towards, for instance, essential amino- and fatty acids, vitamins, taste,... Genome-scale metabolic models combined with flux balance analysis will facilitate this, narrowing down experimental variations and enabling to get the most out of the 'best' combinations of strain and electron and carbon sources.

Microbial community-based protein production from wastewater for animal feed applications

Single cell protein (SCP) derived from microbial biomass represents a promising source of protein for animal feed additives. While microbial community-based approaches to SCP production using nutrient-rich wastewaters incur lower costs than traditional single organism-based approaches, they have received little attention. This review focuses on SCP production using wastewaters with an emphasis on food-processing wastewaters. An elemental carbon-to-nitrogen ratio ranging from 10 to 20 is recommended to promote a high microbial biomass protein yield. Proteobacteria was identified as the most prevalent phylum within SCP-producing microbial communities. More research is needed to determine the composition of the microbial community best suited for SCP production, as well as its relationship with the microbial community in influent food-processing wastewaters. Remaining challenges are target protein and essential amino acids content, protein quantification and biomass yield assessment. The review presents bioreactor design considerations towards defining suitable operating conditions for SCP production through microbial community-based fermentation.