Biosynthesis of Silver and Gold Nanoparticles and Their Efficacy Towards Antibacterial, Antibiofilm, Cytotoxicity, and Antioxidant Activities.

The World Health Organization (WHO) reports that the emergence of multidrug-resistant and the slow advent of novel and more potent antitumor and antimicrobial chemotherapeutics continue to be of the highest concern for human health. Additionally, the stability, low solubility, and negative effects of existing drugs make them ineffective. Studies into alternative tactics to tackle such tenacious diseases was sparked by anticancer and antibacterial. Silver (Ag) and gold (Au) nanoparticles (NPs) were created from Trichoderma saturnisporum, the much more productive fungal strain. Functional fungal extracellular enzymes and proteins carried out the activities of synthesis and capping of the generated nano-metals. Characterization was done on the obtained Ag-NPs and Au-NPs through UV-vis, FTIR, XRD, TEM, and SEM. Additionally, versus methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, and Klebsiella pneumoniae, the antibacterial activities of Ag-NPs and Au-NPs were assessed. In particular, the Ag-NPs were more effective against pathogenic bacteria than Au-NPs. Furthermore, antibiofilm study that shown Au-NPs had activity more than Ag-NPs. Interestingly, applying the DPPH procedure, these noble metallic NPs had antioxidant activity, in which the IC50 for Ag-NPs and Au-NPs was 73.5 µg/mL and 190.0 µg/mL, respectively. According to the cytotoxicity evaluation results, the alteration in the cells was shown as loss of their typical shape, partial or complete loss of monolayer, granulation, shrinking, or cell rounding with IC50 for normal Vero cell were 693.68 µg/mL and 661.24 µg/mL, for Ag-NPs and Au-NPs, respectively. While IC50 for cancer cell (Mcf7) was 370.56 µg/mL and 394.79 µg/mL for Ag-NPs and Au-NPs, respectively. Ag-NPs and Au-NPs produced via green synthesis have the potential to be employed in the medical industry as beneficial nanocompounds.

High Improvement in Lactic Acid Productivity by New Alkaliphilic Bacterium Using Repeated Batch Fermentation Integrated with Increased Substrate Concentration.

Optically pure lactic acid (LA) is an important chemical platform that has a wide range of industrial and biotechnological applications. Improved parameters for cost effective LA production are of great interest for industrial developments. In the present study, an alkaliphilic lactic acid bacterium, BoM 1-2, was selected among 369 newly obtained bacterial isolates. It was characterized using API 50 CHL kit and identified as Enterococcus hirae BoM 1-2 by 16S rRNA gene sequence analysis. Efficient polymer-grade L-lactic acid production was achieved at pH 9.0 and 40°C. In batch fermentation strategy using 20 g L-1 glucose, 19.6 g L-1 lactic acid was obtained with volumetric productivity of 2.18 g L-1 h-1. While using 100 g L-1 glucose, 96.0 g L-1 lactic acid was obtained with volumetric productivity of 1.07 g L-1 h-1. The highest lactic acid concentration of 180.6 g L-1 was achieved in multipulse fed batch strategy with volumetric productivity of 0.65 g L-1 h-1. To achieve higher productivity, repeated fermentation processes were applied using the two different strategies. In the first strategy, the lactic acid productivity was increased from 1.97 g L-1 h-1 to 4.48 g L-1 h-1 when the total of 10 repeated runs were carried out using 60 g L-1 glucose, but lactic acid productivity decreased to 2.95 g L-1 h-1 using 100 g L-1 glucose. In second strategy, repeated fermentation coupled with gradual increase in glucose concentration from 40 to 100 g L-1 was conducted for 24 runs. A dramatic increase in LA productivity up to 39.9 g L-1 h-1 (18-fold compared to first run) was achieved using 40 g L-1 glucose while volumetric productivity ranging between 24.8 and 29.9 g L-1 h-1 was achieved using 60-100 g L-1 glucose.