Green recovery of phenolic compounds from almond hull waste using ultrasound-assisted extraction: phenolics characterization and antimicrobial investigation

This research aims to maximize the extraction of phenolic compounds (PCs) from almond hull waste (AHW) using an ultrasound-assisted extraction (UAE) method, detect the PCs, and investigate the antimicrobial activity of the extracts against pathogens and interactions with a probiotic bacterium. The impact of various parameters including sonication amplitude, solvent/AHW ratio (mL/g), and extraction time on the total phenolic content (TPC) was investigated and the optimized extraction conditions were determined. The AHW extracts' minimum bacterial concentration (MBC) and minimum inhibitory concentration (MIC) against Staphylococcus aureus, Escherichia coli, and Lactobacillus plantarum were assessed. In optimal UAE conditions total PCs of 47.37 ± 0.24 mg gallic acid equivalent (GAE)/g dry weight (DW) were extracted. The HPLC analysis revealed that the flavonoid rutin, as well as p-coumaric acid and rosmarinic acid, were only seen in the extracts obtained by UAE. Furthermore, p-coumaric acid emerged as the most prevalent PC in the UAE extract. Antimicrobial activity analysis showed that UAE extracts exhibited higher effects in inhibiting the growth of E. coli, S. aureus, and L. plantarum. The use of UAE treatment resulted in the extraction of a diverse range of PCs with increased antioxidant capacity and antimicrobial activity.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-024-05969-3.

Production and Optimization of Conjugated Linoleic and Eicosapentaenoic Acids by Bifidobacterium lactis in Cold-Pressed Soybean Cake

Background and Purpose

In regard to the biosynthesis of conjugated linoleic acid (CLA) and eicosapentaenoic acid (EPA) by some bacteria, the objective of this study was to evaluate the efficiency of solid-state fermentation based on soybean pressed cake (SPC) to produce CLA and EPA by Bifidobacterium lactis. The objective of this study was to evaluate the efficiency of solid-state fermentation based on SPC to produce CLA and EPA by B. lactis.

Methods

Process conditions including humidity, inoculation level, and temperature parameters were optimized by adopting the response surface methodology (RSM) method (response surface method) and the design expert software. Accordingly, a homogeneous SPC paste substrate at 60, 70, and 80% humidity was prepared with different inoculation levels at 30, 37, and 44°C to assess the strain behavior. The introduced SPC consisted of 60% humidity, 2% inoculation level at 37°C, and 60% humidity, and 4% inoculation level at 30 and 44°C; it also included 6% inoculation level at 37°C, 70% humidity at 2% inoculation level, at 30 and 44°C, and 4% inoculation level at 37°C. Also, SPC with 80% humidity at 2% and 4% inoculation levels, and at 30 and 44°C was obtained. To confirm the accuracy of the conditions, an experiment was conducted according to the defined requirements.

Results

The results were compared with the predicted data, which showed a significant difference. Under optimized conditions, with an inoculation level of 4% on the SPC medium with 70% humidity and at 37°C, B. lactis strains could yield 9cis-, 11 trans-linoleic and eicosapentaenoic at 0.18 and 0.39% of the total fatty acids.

Conclusion

So, the potential benefits of using SPC as an inexpensive substrate for the commercial production of CLA and EPA should be noted.

Effect of Sodium Alginate-Bulk Chitosan/Chitosan Nanoparticle Wall Matrix on the Viability of Lactobacillus plantarum Under Simulated Gastrointestinal Fluids

The viability of probiotic cells decreases during passage through the gastrointestinal tract. The process of probiotics encapsulation with sodium alginate and chitosan polymers was carried out to protect the Lactobacillus plantarum in adverse conditions. Lactobacillus plantarum was entrapped in sodium alginate/chitosan (SA/BChi) and sodium alginate/nano-chitosan (SA/NChi) wall materials. Encapsulating L. plantarum with SA/BChi and SA/NChi resulted in a high encapsulation efficiency % of ~ 86.41 to 91.09%. In addition, coating bacteria cells in encapsulants improved the survivability of the cells under the simulated gastrointestinal fluids by ~ 52.61% in SA/Chi and 58.04% in SA/NChi compared to 29% for unencapsulated forms. Probiotic beads under field emission-scanning electron microscopy (FE-SEM) were morphologically compact with a cracked appearance of SA/NChi beads. The Fourier transform-infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) showed vigorous electrostatic interaction between polymers, as well as the high melting points, which corroborate the previous investigations in the field for using SA/BChi or SA/NChi as a promising encapsulating agent for ameliorating the survivability of probiotics under harsh conditions. The distinctive properties possessed by the two coatings make them excellent candidates for use as polymeric carriers in probiotic delivery systems.