Ultrasound conditioning of Streptococcus thermophilus CNRZ 447: growth, biofilm formation, exopolysaccharide production, and cell membrane permeability

Abstract

Sonication is one of the new and innovative approaches that is being increasingly used in food industry to control fermentation processes and to eradicate spoiling. Recently, this approach has seen new industrial applications such as enhancing microbial productivity. The present study aimed to assess the effects of ultrasound conditioning on the metabolism and extracellular matrix production of Streptococcus thermophilus. Bacterial suspensions were treated in ultrasonic bath (35 kHz, 240/60 W peak/nominal power, 1.8 l capacity) for different time periods (5, 10, 15, 20, 30, 45, and 65 min), and the growth improvement, adhesion ability, biofilm formation, and exopolysaccharide production of the bacterial strain were measured. The bacterial strain exhibited resistance to the treatment, and the conditioning improved the growth, adhesion, membrane permeability, biofilm formation, and exopolysaccharide production ability. An optimal treatment was obtained for 30 minutes of conditioning. An excellent yield of desirable exopolysaccharides (1788 mg glucose equivalent/l) was achieved. Ultrasound conditioning may be used as a potential approach to enhance certain biotechnological properties of industrial microorganisms.

Impact of ultrasonicated Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus and Lactiplantibacillus plantarum AF1 on the safety and bioactive properties of stirred yoghurt during storage

“…The production of EPS by L. bulgaricus strains has been reported previously [46] . For instance, Khadem, Tirtouil, Drabo and Boubakeur [47] also showed that S. thermophilus strain had important potential to produce EPS. They reported that using ultrasound for a certain period of time could increase the production of EPS by this strain.…”

Ultrasound can increase biofilm formation by Lactiplantibacillus plantarum and Bifidobacterium spp.

“…On the other hand, the positive effect on biofilm stability, mainly found on L. plantarum DSM 1055, could also involve other phenomena, like the increased nutrients transport to deeper layers of the biofilm ( Peterson and Pitt, 2000 ; Erriu et al, 2014 ), as well as by a probable effect on membrane permeability, and exopolysaccharide production ( Khadem et al, 2020 ). In fact, it is reliable to assume that a good diffusion of nutrients across biofilm could delay cell aging, and consequently their detachment from the adhesion surface.…”

Improvement of the Lyophilization Survival Rate of Lactobacillus casei via Regulation of Its Surface Substances

“…Bacterial cells were collected, washed twice in saline, and resuspended in 1 M NaCl solution. Then, surface substances, including CPSs and SPs, were stripped with ultrasonic treatment [ 21 ]. By adjusting the operating frequencies and times, the most appropriate conditions were determined in which the bacteria could survive well, and their surface substance would be stripped completely.…”