Journal of Industrial Microbiology & Biotechnology最新文献

Fermentation of pectin-rich biomass by Saccharomyces cerevisiae can produce bioethanol as a fuel replacement to combat carbon dioxide emissions from the combustion of fossil fuels. Saccharomyces cerevisiae UCDFST 09-448 produces its own pectinase enzymes potentially eliminating the need for commercial pectinases during fermentation. This research assessed growth, pectinase activity, and fermentative activity of S. cerevisiae UCDFST 09-448 and compared its performance to an industrial yeast strain, S. cerevisiae XR122N. Saccharomyces cerevisiae UCDFST 09-448's growth was inhibited by osmotic stress (xylose concentrations above 1 M), ethanol concentrations greater than 5% v/v, and temperatures outside of 30°C-37°C. However, S. cerevisiae UCDFST 09-448 was able to consistently grow in an industrial pH range (3-6). It was able to metabolize glucose, sucrose, and fructose but was unable to metabolize arabinose, xylose, and galacturonic acid. The pectinase enzyme produced by S. cerevisiae UCDFST 09-448 was active under typical fermentation conditions (35°C-37°C, pH 5.0). Regardless of S. cerevisiae UCDFST 09-448's limitations when compared to S. cerevisiae XR122N in 15% w/v peach fermentations, S. cerevisiae UCDFST 09-448 was still able to achieve maximum ethanol yields in the absence of commercial pectinases (44.7 ± 3.1 g/L). Under the same conditions, S. cerevisiae XR122N produced 39.5 ± 3.1 g/L ethanol. While S. cerevisiae UCDFST 09-448 may not currently be optimized for industrial fermentations, it is a step toward a consolidated bioprocessing approach to fermentation of pectin-rich biomass.

One-sentence summary: Saccharomyces cerevisiae UCDFST 09-448 demonstrates the potential to ferment pectin-rich biomass as part of a consolidated bioprocess, but is sensitive to industrial stressors.

Amylosucrase (EC 2.4.1.4) is a versatile enzyme with significant potential in biotechnology and food production. To facilitate its efficient preparation, a novel expression strategy was implemented in Bacillus licheniformis for the secretory expression of Neisseria polysaccharea amylosucrase (NpAS). The host strain B. licheniformis CBBD302 underwent genetic modification through the deletion of sacB, a gene responsible for encoding levansucrase that synthesizes extracellular levan from sucrose, resulting in a levan-deficient strain, B. licheniformis CBBD302B. Neisseria polysaccharea amylosucrase was successfully expressed in B. licheniformis CBBD302B using the highly efficient Sec-type signal peptide SamyL, but its extracellular translocation was unsuccessful. Consequently, the expression of NpAS via the twin-arginine translocation (TAT) pathway was investigated using the signal peptide SglmU. The study revealed that NpAS could be effectively translocated extracellularly through the TAT pathway, with the signal peptide SglmU facilitating the process. Remarkably, 62.81% of the total expressed activity was detected in the medium. This study marks the first successful secretory expression of NpAS in Bacillus species host cells, establishing a foundation for its future efficient production.

One-sentence summary: Amylosucrase was secreted in Bacillus licheniformis via the twin-arginine translocation pathway.

This publication highlights the latest advancements in the field of energy and nutrient recovery from organics rich municipal and industrial waste and wastewater. Energy and carbon rich waste streams are multifaceted, including municipal solid waste, industrial waste, agricultural by-products and residues, beached or residual seaweed biomass from post-harvest processing, and food waste, and are valuable resources to overcome current limitations with sustainable feedstock supply chains for biorefining approaches. The emphasis will be on the most recent scientific progress in the area, including the development of new and innovative technologies, such as microbial processes and the role of biofilms for the degradation of organic pollutants in wastewater, as well as the production of biofuels and value-added products from organic waste and wastewater streams. The carboxylate platform, which employs microbiomes to produce mixed carboxylic acids through methane-arrested anaerobic digestion, is the focus as a new conversion technology. Nutrient recycling from conventional waste streams such as wastewater and digestate, and the energetic valorization of such streams will also be discussed. The selected technologies significantly contribute to advanced waste and wastewater treatment and support the recovery and utilization of carboxylic acids as the basis to produce many useful and valuable products, including food and feed preservatives, human and animal health supplements, solvents, plasticizers, lubricants, and even biofuels such as sustainable aviation fuel.

One-sentence summary: Multifaceted waste streams as the basis for resource recovery are essential to achieve environmental sustainability in a circular economy, and require the development of next-generation waste treatment technologies leveraging a highly adaptive mixed microbial community approach to produce new biochemicals, biomaterials, and biofuels from carbon-rich organic waste streams.

d-Xylose is a metabolizable carbon source for several non-Saccharomyces species, but not for native strains of S. cerevisiae. For the potential application of xylose-assimilating yeasts in biotechnological processes, a deeper understanding of pentose catabolism is needed. This work aimed to investigate the traits behind xylose utilization in diverse yeast species. The performance of 9 selected xylose-metabolizing yeast strains was evaluated and compared across 3 oxygenation conditions. Oxygenation diversely impacted growth, xylose consumption, and product accumulation. Xylose utilization by ethanol-producing species such as Spathaspora passalidarum and Scheffersomyces stipitis was less affected by oxygen restriction compared with other xylitol-accumulating species such as Meyerozyma guilliermondii, Naganishia liquefaciens, and Yamadazyma sp., for which increased aeration stimulated xylose assimilation considerably. Spathaspora passalidarum exhibited superior conversion of xylose to ethanol and showed the fastest growth and xylose consumption in all 3 conditions. By performing assays under identical conditions for all selected yeasts, we minimize bias in comparisons, providing valuable insight into xylose metabolism and facilitating the development of robust bioprocesses.

One-sentence summary: This work aims to expand the knowledge of xylose utilization in different yeast species, with a focus on how oxygenation impacts xylose assimilation.

Spent coffee grounds (SCG) are commercial waste that are still rich in numerous valuable ingredients and can be further processed into useful products such as coffee oil, antioxidant extract, lactic acid, and lignin. The challenge and innovation is to develop the SCG processing technology, maximizing the use of raw material and minimizing the use of other resources within the sequential process. The presented research is focused on the aspect of biotechnological production of lactic acid from SCG by using the Lacticaseibacillus rhamnosus strain isolated from the environment. Thanks to the optimization of the processes of acid hydrolysis, neutralization, enzymatic hydrolysis of SCG, and fermentation, the obtained concentration of lactic acid was increased after 72 hr of culture from the initial 4.60 g/l to 48.6 g/l. In addition, the whole process has been improved, taking into account the dependence on other processes within the complete SCG biorefinery, economy, energy, and waste aspects. Costly enzymatic hydrolysis was completely eliminated, and it was proven that supplementation of SCG hydrolysate with expensive yeast extract can be replaced by cheap waste from the agri-food industry.

One-sentence summary: A process for efficient lactic acid production from spent coffee grounds using the Lacticaseibacillus rhamnosus strain was developed and optimized, including nutrient solution preparation, supplementation and fermentation.

Monoterpene indole alkaloids (MIAs) are a class of natural products comprised of thousands of structurally unique bioactive compounds with significant therapeutic values. Due to difficulties associated with isolation from native plant species and organic synthesis of these structurally complex molecules, microbial production of MIAs using engineered hosts are highly desired. In this work, we report the engineering of fully integrated Saccharomyces cerevisiae strains that allow de novo access to strictosidine, the universal precursor to thousands of MIAs at 30-40 mg/L. The optimization efforts were based on a previously reported yeast strain that is engineered to produce high titers of the monoterpene precursor geraniol through compartmentalization of mevalonate pathway in the mitochondria. Our approaches here included the use of CRISPR-dCas9 interference to identify mitochondria diphosphate transporters that negatively impact the titer of the monoterpene, followed by genetic inactivation; the overexpression of transcriptional regulators that increase cellular respiration and mitochondria biogenesis. Strain construction included the strategic integration of genes encoding both MIA biosynthetic and accessory enzymes into the genome under a variety of constitutive and inducible promoters. Following successful de novo production of strictosidine, complex alkaloids belonging to heteroyohimbine and corynantheine families were reconstituted in the host with introduction of additional downstream enzymes. We demonstrate that the serpentine/alstonine pair can be produced at ∼5 mg/L titer, while corynantheidine, the precursor to mitragynine can be produced at ∼1 mg/L titer. Feeding of halogenated tryptamine led to the biosynthesis of analogs of alkaloids in both families. Collectively, our yeast strain represents an excellent starting point to further engineer biosynthetic bottlenecks in this pathway and to access additional MIAs and analogs through microbial fermentation.

One sentence summary: An Saccharomyces cerevisiae-based microbial platform was developed for the biosynthesis of monoterpene indole alkaloids, including the universal precursor strictosidine and further modified heteroyohimbine and corynantheidine alkaloids.

The growing prevalence of fungal infections alongside rising resistance to antifungal drugs poses a significant challenge to public health safety. At the close of the 2000s, major pharmaceutical firms began to scale back on antimicrobial research due to repeated setbacks and diminished economic gains, leaving only smaller companies and research labs to pursue new antifungal solutions. Among various natural sources explored for novel antifungal compounds, antifungal peptides (AFPs) emerge as particularly promising. Despite their potential, AFPs receive less focus than their antibacterial counterparts. These peptides have been sourced extensively from nature, including plants, animals, insects, and especially bacteria and fungi. Furthermore, with advancements in recombinant biotechnology and computational biology, AFPs can also be synthesized in lab settings, facilitating peptide production. AFPs are noted for their wide-ranging efficacy, in vitro and in vivo safety, and ability to combat biofilms. They are distinguished by their high specificity, minimal toxicity to cells, and reduced likelihood of resistance development. This review aims to comprehensively cover AFPs, including their sources-both natural and synthetic-their antifungal and biofilm-fighting capabilities in laboratory and real-world settings, their action mechanisms, and the current status of AFP research.

One-sentence summary: This comprehensive review of AFPs will be helpful for further research in antifungal research.

There is a growing interest in developing a methodology for effectively cleaving carbon-carbon (C-C) bonds in polymer backbones through bioconversion processes that utilize microorganisms and their enzymes. This upsurge of interest is driven by the goal of achieving a circular economy. Polyolefin post-consumer plastics are a substantial source of carbon, but the recycling potential is severely limited. Upcycling routes are needed for converting polyolefin post-consumer plastics into value-added products while concurrently mitigating adverse environmental effects. These materials contain carbon-based chemicals that can, in principle, serve as the feedstock for microbial metabolism. Some microbes have been reported to grow on polyolefin plastics, but the rate of biodegradation is insufficient for industrial processes. In this study, low-density polyethylene (LDPE) films were subjected to two mild ozone-based oxidation treatments, which facilitated biodegradation. The degree of oxidation was determined by Fourier transform infrared spectroscopy via analysis of the carbonyl index (1,710/1,460 cm-1), which ranged from 0.3 to 2.0, and also via analysis of the carboxylic acid content. Following oxidation of the films, studies were conducted to investigate the ability of a panel of polyvinyl alcohol-degrading microbes to degrade the oxidized films. A defined minimal medium was used to cultivate and assess microbial growth on the oxidized films. Following 45 days of cultivation, the most effective strains were further cultivated up to three additional generations on the oxidized film substrates to improve their ability to degrade the oxidized LDPE films. After these enrichments, we identified a strain from the third generation of Pseudomonas sp. Rh926 that exhibited significant cell growth and reduced the oxidized LDPE film mass by 25% in 30 days, demonstrating an enhanced capacity for degrading the oxidized LDPE films.

One-sentence summary: Discovery and adaptation techniques were used to enhance the metabolic capability of microorganisms for increased biodegradation of ozone-oxidized LDPE films as a step toward a future upcycling process.

The filamentous fungus Trichoderma reesei is a mesophilic ascomycete commercially used to produce industrial enzymes for a variety of applications. Strain improvement efforts over many years have resulted not only in more productive hosts, but also in undesirable traits such as the need for lower temperatures to achieve maximum protein secretion rates. Lower fermentation temperatures increase the need for cooling resulting in higher manufacturing costs. We used a droplet-based evolution strategy to increase the protein secretion temperature of a highly productive T. reesei whole cellulase strain from 25°C to 28°C by first isolating an improved mutant and subsequently tracing the causative high-temperature mutation to one gene designated gef1. An industrial host with a gef1 deletion was found to be capable of improved productivity at higher temperature under industrially relevant fermentation conditions.

One-sentence summary: High-temperature droplet-based evolution resulted in the identification of a mutation in Trichoderma reesei gef1 enabling high productivity at elevated temperatures.