Enhancing small-scale acetification processes using adsorbed Acetobacter pasteurianus UMCC 2951 on κ-carrageenan-coated luffa sponge.

Background: This study explored the utilization of luffa sponge (LS) in enhancing acetification processes. LS is known for having high porosity and specific surface area, and can provide a novel means of supporting the growth of acetic acid bacteria (AAB) to improve biomass yield and acetification rate, and thereby promote more efficient and sustainable vinegar production. Moreover, the promising potential of LS and luffa sponge coated with κ-carrageenan (LSK) means they may represent effective alternatives for the co-production of industrially valuable bioproducts, for example bacterial cellulose (BC) and acetic acid. Methods: LS and LSK were employed as adsorbents for Acetobacter pasteurianus UMCC 2951 in a submerged semi-continuous acetification process. Experiments were conducted under reciprocal shaking at 1 Hz and a temperature of 32 °C. The performance of the two systems (LS-AAB and LSK-AAB respectively) was evaluated based on cell dry weight (CDW), acetification rate, and BC biofilm formation. Results: The use of LS significantly increased the biomass yield during acetification, achieving a CDW of 3.34 mg/L versus the 0.91 mg/L obtained with planktonic cells. Coating LS with κ-carrageenan further enhanced yield, with a CDW of 4.45 mg/L. Acetification rates were also higher in the LSK-AAB system, reaching 3.33 ± 0.05 g/L d as opposed to 2.45 ± 0.05 g/L d for LS-AAB and 1.13 ± 0.05 g/L d for planktonic cells. Additionally, BC biofilm formation during the second operational cycle was more pronounced in the LSK-AAB system (37.0 ± 3.0 mg/L, as opposed to 25.0 ± 2.0 mg/L in LS-AAB). Conclusions: This study demonstrates that LS significantly improves the efficiency of the acetification process, particularly when enhanced with κ-carrageenan. The increased biomass yield, accelerated acetification, and enhanced BC biofilm formation highlight the potential of the LS-AAB system, and especially the LSK-AAB variant, in sustainable and effective vinegar production. These systems offer a promising approach for small-scale, semi-continuous acetification processes that aligns with eco-friendly practices and caters to specialized market needs. Finally, this innovative method facilitates the dual production of acetic acid and bacterial cellulose, with potential applications in biotechnological fields.

Enhanced high ß-carotene yeast cell production by Rhodotorula paludigena CM33 and in vitro digestibility in aquatic animals.

This study assessed Rhodotorula paludigena CM33's growth and ß-carotene production in a 22-L bioreactor for potential use as an aquatic animal feed supplement. Optimizing the feed medium's micronutrient concentration for high-cell-density fed-batch cultivation using glucose as the carbon source yielded biomass of 89.84 g/L and ß-carotene concentration of 251.64 mg/L. Notably, using sucrose as the carbon source in feed medium outperforms glucose feeds, resulting in a ß-carotene concentration of 285.00 mg/L with a similar biomass of 87.78 g/L. In the fed-batch fermentation using Sucrose Feed Medium, R. paludigena CM33 exhibited high biomass production rates (Qx) of 0.91 g/L.h and remarkable ß-carotene production rates (Qp) of 2.97 mg/L.h. In vitro digestibility assays showed that R. paludigena CM33, especially when cultivated using sucrose, enhances protein digestibility affirming its suitability as an aquatic feed supplement. Furthermore, R. paludigena CM33's nutrient-rich profile and probiotic potential make it an attractive option for aquatic nutrition. This research highlights the importance of cost-effective carbon sources in large-scale ß-carotene production for aquatic animal nutrition.

Antimicrobial resistance: more than 70 years of war between humans and bacteria.

Development of antibiotic resistance in bacteria is one of the major issues in the present world and one of the greatest threats faced by mankind. Resistance is spread through both vertical gene transfer (parent to offspring) as well as by horizontal gene transfer like transformation, transduction and conjugation. The main mechanisms of resistance are limiting uptake of a drug, modification of a drug target, inactivation of a drug, and active efflux of a drug. The highest quantities of antibiotic concentrations are usually found in areas with strong anthropogenic pressures, for example medical source (e.g., hospitals) effluents, pharmaceutical industries, wastewater influents, soils treated with manure, animal husbandry and aquaculture (where antibiotics are generally used as in-feed preparations). Hence, the strong selective pressure applied by antimicrobial use has forced microorganisms to evolve for survival. The guts of animals and humans, wastewater treatment plants, hospital and community effluents, animal husbandry and aquaculture runoffs have been designated as "hotspots for AMR genes" because the high density of bacteria, phages, and plasmids in these settings allows significant genetic exchange and recombination. Evidence from the literature suggests that the knowledge of antibiotic resistance in the population is still scarce. Tackling antimicrobial resistance requires a wide range of strategies, for example, more research in antibiotic production, the need of educating patients and the general public, as well as developing alternatives to antibiotics (briefly discussed in the conclusions of this article).

Increasing the acetification rate of Acetobacter aceti adsorbed on luffa sponge using recycle of incremental oxygenated medium.

Speeding up the production of vinegar from rice wine by acetification, using a packed-bed bioreactor with a luffa sponge matrix (LSM) as adsorption carrier of acetic acid bacteria (AAB), and the effect of oxygenation of the recycled medium were investigated. The 0.06 L/min recycle of medium resulted in a high oxygen-transfer coefficient, while optimal dissolved oxygen (DO) of the medium maximized planktonic AAB cell growth with no contamination due to high acid in an external reservoir without LSM. The highest acetification rate (ETA) of 2.857 ± 0.1 g/L/day was achieved with DO 3.5-4.5 ppm at 35 ± 1 °C. To increase ETA, the optimized oxygenated medium was externally supplied and recycled at the ratio of 0.1. Therefore, acetification was conducted in both the bioreactor and reservoir resulting in an increased ETA (6 ± 0.2 g/L/day). This also aligned with the highest system AAB biomass (confirmed by scanning electron microscopy). Under the recycled oxygenated medium supply consistently high biotransformation yields (average 77.3%) were observed over nine sequential cycles. Meanwhile, an average ETA of 6.3 ± 0.2 g/L/day was obtained. This method can have practical applications in improving the efficiency and speeding up small-scale vinegar production.

Alicyclobacillus spoilage and control - a review.

In the last few decades Gram positive non pathogenic, rod shaped, thermo-acidophilic and acid-tolerant spore-forming bacteria such as Alicyclobacillus spp. have been identified as the causative agent in spoilage of commercially pasteurized fruit juice. In particular, A. acidoterrestris is considered a major producer of off-flavors. The spores of A. acidoterrestris possess the ability to survive commercial pasteurization processes, to germinate and grow in low pH environments and to produce volatile, unpleasant odorous compound (guaiacol) in fruit juices. The flat sour type of spoilage (without gas production or package swelling) is characterized as having a "medicinal," "smoky," and "antiseptic" off-flavor and makes the final juice product unacceptable. Spoilage by Alicyclobacillus is a major concern for producers since many of the new methods, which can destroy spores in the absence of chemical additives, may not destroy Alicyclobacillus. Although A. acidoterrestris is not pathogenic to humans, it can result in significant economic losses to juice processors because of its odor. The present review includes the taxonomy of Alicyclobacillus spp., their general characteristics, their resistance to heat and possible off-flavor production pathways. Particular emphasis is given to commonly used control measures, including physical, chemical and biological treatments currently available for removal of Alicyclobacillus spp.

Repeated cultures of Saccharomyces cerevisiae SC90 to tolerate inhibitors generated during cassava processing waste hydrolysis for bioethanol production.

Large amount of cassava pulp is produced as by-product of industrial tapioca production. The value-added process of this low-cost waste is to use it as a substrate for bioethanol production. However, during the pulp pretreatment by acidification combined with steam explosion, many yeast inhibitors including acetic acid, formic acid, levulinic acid, furfural and 5-hydroxymethylfurfural are generated and these compounds have negative effects on the subsequent fermentation step. Therefore, the objective of this study was to investigate whether the repeated cultures of Saccharomyces cerevisiae SC90 could alleviate this problem. To obtain the inhibitor tolerable cells, the repeated culture was performed by growing yeast cells to a specific growth rate (µ) of 0.22 h-1 or higher (80% of the µ in control) and then transferring them to progressively higher concentrations of hydrolysate ranging from 20 to 100% (v/v). The results showed a tendency of longer lag phase as well as time to reach maximum cell number (t maxc) with an increase in hydrolysate concentration. However, the repeated culture at the same hydrolysate concentration could shorten both lag period and t maxc. Interestingly, the growth and fermentation efficiency of adapted cells in 100% hydrolysate were significantly higher (p ≤ 0.05) than those of non-adapted cells by 38% and 27%, respectively.