Grand Challenges in Microbiotechnology: Through the Prism of Microbiotechnology

Optimal fermentation of Pseudomonas synxantha M1 and metabolomics analysis

The microbial agents based on plant growth promoting rhizobacteria (PGPR) have become a hot topic in agricultural research, while the optimization of fermentation conditions for PGPR-based microbial agents still lack systematic research. The single-factor and orthogonal experiments were conducted to determine the optimal fermentation conditions of Pseudomonas synxantha M1. The results indicated that the glycerol and shaker speed was the most significant factors that influence the number of bacteria of P. synxantha M1 fermentation liquid. The viable bacteria count of microbial agent reached 7.1 × 1012 cfu/mL at 36 h, which OD600 value increased by 116.40% compared to before optimization, and promote the growth of highland barley. Significant differences of metabolites of fermentation liquid was observed in different fermentation times, including organic acids, lipids, and organoheterocyclic compounds using liquid chromatography tandem mass spectrometry (LC-MS/MS). In addition, the fermentation liquid was found to contain indoleacetic acid, glutathione and xanthine at the end of fermentation, which might contribute for the growth of plants as bioactive substances.

Gradient boosted regression as a tool to reveal key drivers of temporal dynamics in a synthetic yeast community

Microbial communities are vital to our lives, yet their ecological functioning and dynamics remain poorly understood. This understanding is crucial for assessing threats to these systems and leveraging their biotechnological applications. Given that temporal dynamics are linked to community functioning, this study investigated the drivers of community succession in the wine yeast community. We experimentally generated population dynamics data and used it to create an interpretable model with a gradient boosted regression tree approach. The model was trained on temporal data of viable species populations in various combinations, including pairs, triplets, and quadruplets, and was evaluated for predictive accuracy and input feature importance. Key findings revealed that the inoculation dosage of non-Saccharomyces species significantly influences their performance in mixed cultures, while Saccharomyces cerevisiae consistently dominates regardless of initial abundance. Additionally, we observed multispecies interactions where the dynamics of Wickerhamomyces anomalus were influenced by Torulaspora delbrueckii in pairwise cultures, but this interaction was altered by the inclusion of S. cerevisiae. This study provides insights into yeast community succession and offers valuable machine learning-based analysis techniques applicable to other microbial communities, opening new avenues for harnessing microbial communities.

Bacterial wax synthesis

Biological wax esters offer a sustainable, renewable and biodegradable alternative to many fossil fuel derived chemicals including plastics and paraffins. Many species of bacteria accumulate waxes with similar structure and properties to highly desirable animal and plant waxes such as Spermaceti and Jojoba oils, the use of which is limited by resource requirements, high cost and ethical concerns. While bacterial fermentations overcome these issues, a commercially viable bacterial wax production process would require high yields and renewable, affordable feedstock to make it economically competitive and environmentally beneficial. This review describes recent progress in wax ester generation in both wild type and genetically engineered bacteria, with a focus on comparing substrates and quantifying obtained waxes. The full breadth of wax accumulating species is discussed, with emphasis on species generating high yields and utilising renewable substrates. Key areas of the field that have, thus far, received limited attention are highlighted, such as waste stream valorisation, mixed microbial cultures and efficient wax extraction, as, until effectively addressed, these will slow progress in creating commercially viable wax production methods.