Innovations in process engineering approaches for enhanced bacteriocin production

The intent of this study was to evaluate the symbiotic effectiveness of common bean (Phaseolus vulgaris L.)-nodulating mutant rhizobia isolates to extreme pH and high salt soil condition around Babile, eastern Ethiopia.After mutagenesis, from 50 identified wild rhizobia isolates, a total of 8 mutants were selected based on their ability to survive at extreme salt and pH conditions.The nodule number of mutants were positively and significantly correlated with nodule dry weight (r=0.85,p<0.0001) on sand culture.Six of the highly effective mutants were tested on unsterilized soil in controlled growth chamber.The correlation data on soil experiment displayed that nodule number was positively associated and significant (r=0.73,p<0.0001) with nodule dry weight (NDW) while shoot dry weight (SDW) was positively correlated with present N (r=0.8,p<0.0001) and total nitrogen content (r=0.9, p<0.0001).Physiological test of mutants also showed that-5 (63%) and 3 (36%) of mutants were able to grow at salt concentrations of 11% and 12%, respectively.Notably, 3 (38%), 4 (50%), 2 (25%), and 2 (13%) of the mutants were able to grow at pH 4, 11, 11.5 and 12, respectively.Only the mutant isolates HUCRM2D (which tolerated 12% NaCl, pH4, and pH12), HUCRM5C (which tolerated 12% NaCl and pH 4), HUCRM3B (which tolerated 12% NaCl) and HUCRM9C (which tolerated 11% NaCl) were growing successfully at the indicated extreme conditions.Thus, on the basis of their symbiotic effectiveness and tolerance to extreme environmental conditions, these mutant isolates were recommended to be used as candidates for future development of rhizobial inoculants of common bean grown under saline and extreme pH conditions.

Pesticides are used indiscriminately all over the world to protect crops from pests and pathogens. If they are used in excess, they contaminate the soil and water bodies and negatively affect human health and the environment. However, bioremediation is the most viable option to deal with these pollutants, but it has certain limitations. Therefore, harnessing the role of microbial biosurfactants in pesticide remediation is a promising approach. Biosurfactants are the amphiphilic compounds that can help to increase the bioavailability of pesticides, and speeds up the bioremediation process. Biosurfactants lower the surface area and interfacial tension of immiscible fluids and boost the solubility and sorption of hydrophobic pesticide contaminants. They have the property of biodegradability, low toxicity, high selectivity, and broad action spectrum under extreme pH, temperature, and salinity conditions, as well as a low critical micelle concentration (CMC). All these factors can augment the process of pesticide remediation. Application of metagenomic and in-silico tools would help by rapidly characterizing pesticide degrading microorganisms at a taxonomic and functional level. A comprehensive review of the literature shows that the role of biosurfactants in the biological remediation of pesticides has received limited attention. Therefore, this article is intended to provide a detailed overview of the role of various biosurfactants in improving pesticide remediation as well as different methods used for the detection of microbial biosurfactants. Additionally, this article covers the role of advanced metagenomics tools in characterizing the biosurfactant producing pesticide degrading microbes from different environments.

An effective biosurfactant-producing bacteria, isolate L5, was isolated from mangrove sediments from both east coast and west coast of Southern of Thailand. Analysis of the 16S rRNA gene sequence confirmed that isolate L5 was Agrobacterium rubi with 100% homology. The biosurfactant production was performed using a mineral salt medium (MSM) with molasses as a carbon and commercial monosodium glutamate (MSG) as nitrogen sources. Under optimized conditions, A.rubi L5 was able to grow and produce biosurfactant with the yield of 4.62 g/l at 54 h of cultivation. It could reduce the surface tension of pure water from 72.0 to 25.5 mN/m and exhibit emulsification activity toward palm oil with 65.4%. The biosurfactant found to be stable even under extreme pH, temperature and salinity conditions. The results revealed the potential use of a biosurfactant produced by A. rubi L5 to enhance mobilization sorbed motor oil from environment in comparison with those of synthetic surfactants, i.e. a nonionic surfactant Tween 80 and anionic surfactants sodium dodecyl sulfate.

Biosurfactants (BSs) are natural, biodegradable compounds crucial for replacing synthetic emulsifiers in the food industry, provided their production costs can be reduced through the use of sustainable and low-cost substrates. This study evaluated the viability of licuri oil as a carbon source for BS production by Candida utilis and assessed the product’s functional stability in food formulations. Production kinetics confirmed the yeast’s efficiency, reducing the water surface tension to a minimum of 31.55 mN·m−1 at 120 h. Factorial screening identified a high carbon-to-nitrogen ratio as the key factor influencing ST reduction. The isolated BS demonstrated high surface activity, with a Critical Micelle Concentration of 0.9 g·L−1. Furthermore, the cell-free broth maintained excellent emulsifying activity (E24 &gt; 70%) against canola and motor oils across extreme pH, temperature, and salinity conditions. Twelve mayonnaise-type dressings were formulated, utilizing licuri oil, and tested for long-term physical stability. Six formulations, featuring the BS in combination with lecithin and/or egg yolk, remained stable without phase segregation after 240 days of refrigeration, maintaining a stable pH and suitable microbiological conditions for human consumption. The findings confirm that the valorization of licuri oil provides a route to produce a highly efficient and robust BS, positioning it as a promising co-stabilizer for enhancing the shelf-life and natural appeal of complex food emulsions.

The substantial success of plastic as a material is owed to its unparalleled designs with unique properties and proved versatility in an extensive range of applications. Unfortunately, the reliance on single-use plastic commodities consequently results in the incorrect disposal and accumulation of this waste at staggering rates in our environment and landfill sites. In this regard, there is a vested interest in replacing petrochemical plastics with natural, biodegradable plastics (bioplastics). Of the many natural polymers available, microbially synthesized polyhydroxyalkanoates (PHAs) have gained popularity. Eco-friendly PHA-based bioplastics are characteristically as robust and as durable as their oil-based equivalents. Pulp and paper mill sludge (PPMS) is another solid waste stream that is predominantly disposed of via landfilling. The environmentally hazardous gases and leachate emitted from PPMS together with limited landfill space availability and the implementation of strict waste management legislation may not make landfilling practicable in the future. However, this carbohydrate-rich biomass has favorable traits that make it applicable as a feedstock for microbial biomass and PHA production. Hence, in the interest of addressing the issues mentioned above, this study aimed to beneficiate PPMS into PHAs by applying it as the sole feedstock for microbial cell proliferation and subsequent PHA production. Presently, to the best of the author’s knowledge, there are no reports on PHA production as a route for valorization of PPMS from South African pulp and paper mills. Thus, the novelty of the present study is marked by the unique ways of incorporating PPMS as a low-cost substrate as well as the various fermentative strategies navigated to enhance both microbial cell biomass and PHA productivity. In the present study, it was established that Bacillus thuringiensis had promising PHA-producing capability. The strain synthesized a copolymer and terpolymer using untreated (raw) neutral semi-sulphite chemical pulping and cardboard recycling mill (NSSC-CR) and prehydrolysis kraft and kraft pulping mill (PHKK) PPMS in a consolidated bioprocessing fermentation. A separate hydrolysis and fermentation strategy was pursued whereby a glucose-rich hydrolyzate was obtained from enzymolysis of PPMS and subsequently utilized in a cyclic fed-batch fermentation (CFBF) strategy to obtained enhanced yields of cell biomass and PHAs. Response surface methodology (RSM) was first implemented to optimize the conditions for enzymatic saccharification of de-ashed PHKK PPMS. The optimized variables were; pH 4.89; 51°C; hydrolysis time 22.9 h; 30 U/g β-glucosidase and 60 U/g cellulase; and 6.4% of dried de-ashed PPMS fiber resulting in a hydrolyzate comprising of 48.27% glucose. Thereafter, CFBF was pursued where the glucose-rich hydrolyzate was employed as the sole carbon source for cell proliferation and PHA production. The statistically optimized fermentation conditions to obtain high cell density biomass (OD600 of 2.42) were; 8.77 g L-1 yeast extract; 66.63% hydrolyzate (v/v); a fermentation pH of 7.18; and an incubation time of 27.22 h. The CFBF comprised of three cycles and after the third cyclic event, maximum cell biomass (20.99 g L-1) and PHA concentration (14.28 g L-1) were achieved. This cyclic strategy yielded an almost 3-fold increase in biomass concentration and a 4-fold increase in PHA concentration compared with batch fermentation. The properties of the synthesized PHAs were similar to commercial polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-valerate (PHBV) and also displayed slightly higher thermostability and lower crystallinity compared with commercial PHB and PHBV. This is the first report detailing the proof of concept of using PPMS from South African pulp and paper making mills for cell biomass and PHA production by B. thuringiensis. In addition, this study reports on the practicality and novelty of utilizing PPMS either in its raw, untreated state or as enzymatically saccharified glucose-rich hydrolyzate as cheap substrates applicable for both cell biomass and PHA production using different fermentation strategies. Finally, to the best of our knowledge, this is also the first report that has successfully applied B. thuringiensis in a CFBF strategy coupled with glucose-rich hydrolyzate as the sole carbon source for the production of high cell density biomass and enhanced PHA production. From this study, it is intended that innovative insights and prospective solutions to valorizing pulp and paper mill sludge are provided, whilst simultaneously generating a value-added product.

Fed-batch fermentation of Mucor circinelloides reveals significant improvement in biomass and lipid accumulation through performance evaluation, chemical analysis, and expression profiling

The growing consumer demand for natural food preservatives has intensified research into bacteriocins, due to their potential to enhance food safety and preservation. This study aimed to conduct a bibliometric analysis of bacteriocin research from 2003 to 2023, focusing on their applications in food preservation to identify critical trends, challenges, and future directions. The analysis revealed a significant publication increase with an annual growth rate of 9.89% with countries like China, Brazil, and India as the leaders in contributions. Also, journals like “Food Control” and “Journal of Applied Microbiology” were major dissemination platforms. The research predominantly fell under Food Science Technology and Microbiology, with foundational studies by Leverentz et al. and Hammami et al. receiving high citations. Despite challenges such as pH sensitivity, thermal stability, and regulatory hurdles, advances in nanotechnology and collaborative global research are enhancing bacteriocin stability and efficacy. The study also identified emerging research themes, including integrating bacteriocins into antimicrobial packaging and their combination with other antimicrobial agents. The findings underscore the potential of bacteriocins as natural preservatives, driven by consumer demand for minimally processed foods and the need for sustainable food preservation strategies. In conclusion, while bacteriocins show promise, overcoming application and regulatory challenges is necessary for their broader integration into food safety strategies, aligning to promote sustainable and effective food preservation solutions.

Biosurfactants are amphiphilic molecules produced by a variety of microorganisms, including bacteria, yeast and filamentous fungi. Unlike chemically synthesized surfactants, biosurfactants present advantages, such as biodegradability, low toxicity, high selectivity and activity under extreme temperature, pH and salinity conditions, as well as a low critical micelle concentration. Moreover, they can be produced from agro-industrial waste and renewable sources. Their structural diversity and functional properties mean that they have potential applications in various industrial processes as wetting agents, dispersants, emulsifiers, foaming agents, food additives and detergents, as well as in the field of environmental biotechnology. However, opportunities for their commercialization have been limited due to the low yields obtained in the fermentation processes involved in their production as well as the use of refined raw materials, which means higher cost in production. In an attempt to solve these limitations on the commercialization of biosurfactants, various research groups have focused on testing the use of inexpensive alternative sources, such as agro-industrial waste, as substrates for the production of different biosurfactants. In addition to enabling the economical production of biosurfactants, the use of such waste aims to reduce the accumulation of compounds that cause environmental damage. This review shows advances in biosurfactant production carried out using different waste materials or by-products from agro-industrial activities.

The Sustainable Development Goals (SDGs) emphasize the importance of food safety, prolonged shelf life, and reduced food waste, all of which rely on effective food preservation methods. Bacteriocins, natural antimicrobial substances produced by lactic acid bacteria (LAB), have potential applications in food preservation. This review highlights the role of LAB-derived bacteriocins in preserving food. Bacteriocins are highly effective against foodborne infections because they target cell membranes, break down enzymes, and interfere with cellular activities. The following study used molecular docking to understand the interaction of bacteriocins and their mode of action. With their natural origin and specific action, bacteriocins offer a promising strategy for preventing foodborne diseases and extending shelf life without impacting sensory characteristics. However, challenges such as stable manufacturing, regulatory hurdles, and cost effectiveness hinder the wide adoption of bacteriocins. Nevertheless, LAB-derived bacteriocins offer a safe and efficient approach to improving food preservation, enhancing food safety, and reducing reliance on artificial preservatives. Moreover, immobilized bacteriocins have the potential to be integrated into antimicrobial packaging films, providing a targeted way to reduce the risk of foodborne pathogen contamination and improve food safety. Exploring novel bacteriocins presents exciting opportunities for advancing food preservation and safety. The present study also highlights recent advancements in food preservation through bacteriocins.

Mannanases, one of the important enzyme group for industry, are produced by numerous filamentous fungi, especially Aspergillus species with different fermentation methods. The aim of this study was to show the best fermentation method of β-mannanase production for fungal growth in fermenter. Therefore, different fermentation strategies in fed-batch fermentation (suspended, immobilized cell, biofilm and microparticle-enhanced bioreactor) were applied for β-mannanase production from glucose medium (GM) and carob extract medium (CEM) by using recombinant Aspergillus sojae. The highest β-mannanase activities were obtained from microparticle-enhanced bioreactor strategy. It was found to be 347.47 U/mL by adding 10g/L of Al2O3 to GM and 439.13 U/mL by adding 1g/L of talcum into CEM. The maximum β-mannanase activities for suspended, immobilization, and biofilm reactor remained at 72.55 U/mL in GM, 148.81 U/mL in CEM, and 194.09 U/mL in GM, respectively. The reason for that is the excessive, and irregular shaped growth and bulk formation, inadequate oxygen transfer or substrate diffusion in bioreactor. Consequently, the enzyme activity was significantly enhanced by addition of microparticles compared to other fed-batch fermentation strategies. Also, repeatable β-mannanase activities were obtained by controlling of the cell morphology by adding microparticle inside the fermenter.

High temperature and high salinity (HTHS) and extreme pH conditions can significantly affect the stability of polymers and deteriorate the performance of polymers in enhanced oil recovery (EOR). This work advances polymer flooding in harsh environments on two fronts: engineering polymers with improved temperature tolerance and dispersing suitable nanoparticles in the synthesized polymers to further improve their capabilities to withstand temperature, salinity, and different pH conditions. Different modified acrylamide copolymers (polymers synthesized from two different monomers) and terpolymers (polymers synthesized from three different monomers) are produced via free-radical polymerization, and multiwall carbon nanotubes (MWCNTs) were introduced to obtain aqueous polymer dispersions with unique properties. The conversion, molecular weight, and polydispersity of the co/terpolymers were evaluated by 1H-NMR and GPC analysis. The interfacial, rheological behavior and stability of the dispersions were investigated under HTHS conditions at various pH values to identify the suitable candidates for EOR applications. The oil recovery performance is examined in a core flooding setup at 85°C and American Petroleum Institute (API) brine conditions. The polyampholytic terpolymer and polyelectrolyte copolymer containing negative sulfonate groups showed improved viscosity and stability in the presence of MWCNTs in alkaline and saline conditions, respectively. Compared to the pure polymer dispersions, the addition of MWCNTs to polymers improves the oil recovery efficiency at high temperature (85 °C) in the presence of both alkaline pH and API brine conditions yet with a lower pressure drop. This shows great promise for future EOR applications.

Atomic force microscopy in food preservation research: New insights to overcome spoilage issues

Archaea have many unique physiological features of which the lipid composition of their cellular membranes is the most striking. Archaeal ether-linked isoprenoidal membranes can occur as bilayers or monolayers, possess diverse polar head groups, and a multiplicity of ring structures in the isoprenoidal cores. These lipid structures are proposed to provide protection from the extreme temperature, pH, salinity, and nutrient-starved conditions that many archaea inhabit. However, many questions remain regarding the synthesis and physiological role of some of the more complex archaeal lipids. In this study, we identify a radical S-adenosylmethionine (SAM) protein in Sulfolobus acidocaldarius required for the synthesis of a unique cyclopentyl head group, known as calditol. Calditol-linked glycerol dibiphytanyl glycerol tetraethers (GDGTs) are membrane spanning lipids in which calditol is ether bonded to the glycerol backbone and whose production is restricted to a subset of thermoacidophilic archaea of the Sulfolobales order within the Crenarchaeota phylum. Several studies have focused on the enzymatic mechanism for the synthesis of the calditol moiety, but to date no protein that catalyzes this reaction has been discovered. Phylogenetic analyses of this putative calditol synthase (Cds) reveal the genetic potential for calditol-GDGT synthesis in phyla other than the Crenarchaeota, including the Korarchaeota and Marsarchaeota. In addition, we identify Cds homologs in metagenomes predominantly from acidic ecosystems. Finally, we demonstrate that deletion of calditol synthesis renders S. acidocaldarius sensitive to extremely low pH, indicating that calditol plays a critical role in protecting archaeal cells from acidic stress.

Biosurfactant production and oil degradation by Bacillus siamensis and its potential applications in enhanced heavy oil recovery

Spices have been used since ancient times. Although they have been employed mainly as flavoring and coloring agents, their role in food safety and preservation have also been studied in vitro and in vivo. Spices have exhibited numerous health benefits in preventing and treating a wide variety of diseases such as cancer, aging, metabolic, neurological, cardiovascular, and inflammatory diseases. The present review aims to provide a comprehensive summary of the most relevant and recent findings on spices and their active compounds in terms of targets and mode of action; in particular, their potential use in food preservation and enhancement of shelf life as a natural bioingredient.