The relationships between microbiota and the amino acids and organic acids in commercial vegetable pickle fermented in rice-bran beds

Influence of the initial microbiota on eggplant shibazuke pickle and eggplant juice fermentation

The present study aimed to investigate the effects of the initial microbiota on microbial succession and metabolite transition during eggplant fermentation. Samples of traditional Japanese eggplant pickles, shibazuke, which were spontaneously fermented by plant-associated microbiota, were used for the analysis. Microbiota analysis indicated two successional patterns: early dominance of lactic acid bacteria superseded by aerobic bacteria and early dominance of lactic acid bacteria maintained to the end of the production process. Next, shibazuke production was modeled using filter-sterilized eggplant juice, fermenting the average composition of the initial shibazuke microbiota, which was artificially constructed from six major species identified during shibazuke production. In contrast to shibazuke production, all batches of eggplant juice fermentation showed almost identical microbial succession and complete dominance of Lactiplantibacillus plantarum in the final microbiota. These findings revealed the fate of initial microbiota under shibazuke production conditions: the early dominance of lactic acid bacteria that was maintained throughout, with L. plantarum ultimately predominating the microbiota. Furthermore, a comparison of the results between shibazuke production and eggplant juice fermentation suggested that L. plantarum is involved in the production of lactic acid, alanine, and glutamic acid during eggplant fermentation regardless of the final microbiota.

IMPORTANCE

The findings shown in this study provide insight into the microbial succession during spontaneous pickle fermentation and the role of Lactiplantibacillus plantarum in eggplant pickle production. Moreover, the novel method of using filter-sterilized vegetable juice with an artificial microbiota to emulate spontaneous fermentation can be applied to other spontaneously fermented products. This approach allows for the evaluation of the effect of specific initial microbiota in the absence of plant-associated bacteria from raw materials potentially promoting a greater understanding of microbial behavior in complex microbial ecosystems during vegetable fermentation.

Fermented Vegetables: Health Benefits, Defects, and Current Technological Solutions

This review summarizes current studies on fermented vegetables, analyzing the changes in nutritional components during pickling, the health benefits of fermented vegetables, and their safety concerns. Additionally, the review provides an overview of the applications of emergent non-thermal technologies for addressing these safety concerns during the production and processing of fermented vegetables. It was found that vitamin C would commonly be lost, the soluble protein would degrade into free amino acids, new nutrient compositions would be produced, and the flavor correlated with the chemical changes. These changes would be influenced by the variety/location of raw materials, the original bacterial population, starter cultures, fermentation conditions, seasoning additions, and post-fermentation processing. Consuming fermented vegetables benefits human health, including antibacterial effects, regulating intestinal bacterial populations, and promoting health (anti-cancer effects, anti-diabetes effects, and immune regulation). However, fermented vegetables have chemical and biological safety concerns, such as biogenic amines and the formation of nitrites, as well as the existence of pathogenic microorganisms. To reduce hazardous components and control the quality of fermented vegetables, unique starter cultures, high pressure, ultrasound, cold plasma, photodynamic, and other technologies can be used to solve these problems.

Marinobacter: A case study in bioelectrochemical chassis evaluation

The junction of bioelectrochemical systems and synthetic biology opens the door to many potentially groundbreaking technologies. When developing these possibilities, choosing the correct chassis organism can save a great deal of engineering effort and, indeed, can mean the difference between success and failure. Choosing the correct chassis for a specific application requires a knowledge of the metabolic potential of the candidate organisms, as well as a clear delineation of the traits, required in the application. In this review, we will explore the metabolic and electrochemical potential of a single genus, Marinobacter. We will cover its strengths, (salt tolerance, biofilm formation and electrochemical potential) and weaknesses (insufficient characterization of many strains and a less developed toolbox for genetic manipulation) in potential synthetic electromicrobiology applications. In doing so, we will provide a roadmap for choosing a chassis organism for bioelectrochemical systems.

Direct contact of fermented rice bran beds promotes food-to-hand transmission of lactic acid bacteria

The skin microbiome, which varies widely between individuals, plays a crucial role in human health. It also interacts with the environment in various ways, including during the preparation of fermented food. Nukadoko is a pickle and traditional fermented food in Japan that utilizes lactic acid bacteria to ferment vegetables. When preparing or maintaining Nukadoko, it is mixed with bare hands. Despite the known interaction between Nukadoko and human skin, no studies have explored its impact on Nukadoko quality or skin microbiome changes. This study examines these effects during Nukadoko maintenance. Three participants were asked to stir commercially available late-stage Nukadoko for 14 days and not stir it for the remaining 14 days to examine microbial settlement and shedding. Microbiome analysis was performed on human skin and Nukadoko. We found that microorganisms from rice bran beds can temporarily settle on human skin but are shed quickly. Stirring rice bran beds by hand may have short-term effects on the skin microbiome. This study provides insights into the communication between human and food microbiomes in traditional Japanese fermented foods.

Nutritional and Volatile Characterisation of Milk Inoculated with Thermo-Tolerant Lactobacillus bulgaricus through Adaptive Laboratory Evolution

In this study, thermo-tolerant strain of Lactobacillus bulgaricus (L. bulgaricus) was developed using gradual increase in temperature to induce Adaptive Laboratory Evolution (ALE). Viable colony count of 1.87 ± 0.98 log cfu/mL was achieved at 52 °C, using MRS agar supplemented with 2% lactose. Changes in bacteria morphology were discovered, from rod (control) to filament (52 °C) to cocci after frozen storage (−80 °C). When milk was inoculated with thermo-tolerant L. bulgaricus, lactic acid production was absent, leaving pH at 6.84 ± 0.13. This has caused weakening of the protein network, resulting in high whey separation and lower water-holding capacity (37.1 ± 0.35%) compared to the control (98.10 ± 0.60%). Significantly higher proteolytic activity was observed through free amino acids analysis by LC-MS. Arginine and methionine (237.24 ± 5.94 and 98.83 ± 1.78 µg/100 g, respectively) were found to be 115- and 275-fold higher than the control, contributing to changing the aroma similar to cheese. Further volatile analysis through SPME-GC-MS has confirmed significant increase in cheese-aroma volatiles compared to the control, with increase in diacetyl formation. Further work on DNA profiling, metabolomics and peptidomics will help to answer mechanisms behind the observed changes made in the study.

Microbial Ecology of French Dry Fermented Sausages and Mycotoxin Risk Evaluation During Storage

Dry fermented sausages are produced worldwide by well-controlled fermentation processes involving complex microbiota including many bacterial and fungal species with key technological roles. However, to date, fungal diversity on sausage casings during storage has not been fully described. In this context, we studied the microbial communities from dry fermented sausages naturally colonized or voluntarily surface inoculated with molds during storage using both culture-dependent and metabarcoding methods. Staphylococci and lactic acid bacteria largely dominated in samples, although some halotolerant genera (e.g., Halomonas, Tetragenococcus, and Celerinatantimonas spp.) were also frequently observed. Fungal populations varied from 7.2 to 9.8 log TFU/cm² sausage casing during storage, suggesting relatively low count variability among products. Fungal diversity identified on voluntarily inoculated casings was lower (dominated by Penicillium nalgiovense and Debaryomyces hansenii) than naturally environment-inoculated fermented sausages (colonized by P. nalgiovense, Penicillium nordicum, and other Penicillium spp. and sporadically by Scopulariopsis sp., D. hansenii, and Candida zeylanoïdes). P. nalgiovense and D. hansenii were systematically identified, highlighting their key technological role. The mycotoxin risk was then evaluated, and in situ mycotoxin production of selected mold isolates was determined during pilot-scale sausage productions. Among the identified fungal species, P. nalgiovense was confirmed not to produce mycotoxins. However, some P. nordicum, Penicillium chrysogenum, Penicillium bialowienzense, Penicillium brevicompactum, and Penicillium citreonigrum isolates produced one or more mycotoxins in vitro. P. nordicum also produced ochratoxin A during pilot-scale sausage productions using “worst-case” conditions in the absence of biotic competition. These data provide new knowledge on fermented sausage microbiota and the potential mycotoxin risk during storage.

Biotechnology for carbon capture and fixation: Critical review and future directions

To mitigate the growing threat of climate change and develop novel technologies that can eliminate carbon dioxide, the most abundant greenhouse gas derived from the flue gas stream of the fossil fuel-fired power stations, is momentous. The development of carbon capture and sequestration-based technologies may play a significant role in this regard. Carbon fixation mostly occurs by photosynthesizing plants as well as photo and chemoautotrophic microbes that turn the atmospheric carbon dioxide into organic materials via their enzymes. Biofuel can offer a sustainable solution for carbon mitigation. The pragmatic implementation of biofuel production processes is neither cost-effective nor has been proven safe over the long term. Searching for ways to enhance biofuel generation by the employment of genetic engineering is vital. Carbon biosequestration can help to curb the greenhouse effect. In addition, new genomic approaches, which are able to use gene-splicing biotechnology techniques and recombinant DNA technology to produce genetically modified organisms, can contribute to improvement in sustainable and renewable biofuel and biomaterial production from microorganisms. Biopolymers, Biosurfactants, and Biochars are suggested as sustainable future trends. This study aims to pave the way for implementing biotechnology methods to capture carbon and decrease the demand and consumption of fossil fuels as well as the emissions of greenhouse gases. Having a better image of microorganisms' potential role in carbon capture and storage can be prolific in developing powerful techniques to reduce CO₂ emissions.