# The use of pulsed ultrasound with reduced power delivery to degrade the polysaccharide curdlan

## TL;DR

Pulsed ultrasound uses less power than continuous ultrasound to efficiently break down the polysaccharide curdlan into more uniform fragments.

## Contribution

Pulsed ultrasound is shown to be more energy-efficient for curdlan degradation with faster and more precise chain cleavage.

## Key findings

- Pulsed ultrasound achieves 60% curdlan degradation in 25 minutes with one-sixth the power of continuous ultrasound.
- Pulsed ultrasound reduces dispersity more rapidly, leading to a more homogeneous solution.
- Chain scission occurs preferentially at midpoints, favoring longer chains and aligning with the midpoint scission model (R² ∼ 0.96).

## Abstract

•Energy-efficient pulsed ultrasound outperforms continuous US in curdlan degradation.•Pulsed US increases polysaccharide molecular weight reduction with less power.•Ultrasonic curdlan degrades via near-midpoint scission, biased toward longer chains.•Ultrasound-induced reduction in dispersity improves curdlan solution homogeneity.

Energy-efficient pulsed ultrasound outperforms continuous US in curdlan degradation.

Pulsed US increases polysaccharide molecular weight reduction with less power.

Ultrasonic curdlan degrades via near-midpoint scission, biased toward longer chains.

Ultrasound-induced reduction in dispersity improves curdlan solution homogeneity.

This study investigated the use of continuous ultrasound and low-power pulsed ultrasound on curdlan degradation by analyzing molecular weight changes during sonication. Although pulsed ultrasound only delivered one-sixth of the power of continuous ultrasound, it led to faster curdlan degradation. The most significant differences occurred within the first 25 min: Pulsed ultrasound accelerated the cleavage of polysaccharide chains, resulting in a degradation rate of approximately 60 % and a substantial reduction in the mass fraction of fragments with a molecular weight exceeding 400 kDa (from ca. 85 % to 3 %). Continuous ultrasound required 65 min to achieve a similar degree of degradation. The decrease in dispersity (from 1.13 to 1.06 within 65 min) indicated the non-random nature of the process, which occurred more rapidly during pulsed ultrasound. The degradation kinetics fit second-order and Ovenall/Harrington/Madras models, favoring pulsed ultrasound, which had a higher rate constant. Analysis of the chain scission mechanism showed a robust correlation between the midpoint scission model and the experimental data (R2 ∼ 0.96). According to the simulation analysis, larger curdlan particles are preferentially degraded, with pulsed ultrasound providing greater precision in cleavage localization. These findings suggest that employing pulsed ultrasound with a reduced power supply is an energy-efficient strategy to obtain more uniform polysaccharides with a moderately reduced molecular weight.