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<p>The coffee industry generates approximately 6 million tons of waste annually, primarily spent coffee grounds (SCGs), whose disposal in landfills poses environmental risks. Therefore, new valorization strategies must be implemented to mitigate their environmental impact. In this sense, the objective of this study was to characterize SCGs and to optimize the dilute sulfuric acid pretreatment process for extracting oligosaccharides (OS). Optimal extraction conditions were determined using response surface methodology (RSM) with a Box-Behnken (BB) 3<sup>3</sup> design that included five central points for improved accuracy. The factors evaluated were temperature (140–190&#xa0;°C), solid/liquid (S/L) ratio (1:40–1:4&#xa0;g/mL), reaction time (20–120&#xa0;min), and sulfuric acid concentration (0–2% v/v). Hemicellulose was identified as the predominant component, consisting mainly of mannose. OS extraction yields varied from 1.65 to 22.40&#xa0;g per 100&#xa0;g dry SCGs, depending on the process conditions. The quadratic model yielded an <i>R</i><sup>2</sup> value of 0.91128, indicating that the S/L ratio was the most influential factor, while reaction time had no significant effect. The optimized conditions—S/L ratio of 1:40 (g/mL), reaction time of 20&#xa0;min, and H₂SO₄ concentration of 1.43% v/v at 168.57&#xa0;°C—were experimentally validated and showed a margin of error of less than 9%. MALDI-TOF–MS analysis revealed oligosaccharide structures composed of hexose and pentose chains with up to eight sugar units. This study advances the understanding of OS extraction from SCGs via dilute acid pretreatment and provides valuable insight into waste valorization through process optimization and engineering approaches.</p>

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Acid hydrolysis pretreatment for extraction of oligosaccharides derived from spent coffee grounds: valorization of a promising biomass

  • 期刊论文

  • 发表日期：

    2025年4月17日

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  • Henrique Maziero Fogarin,
  • Sarha Lucia Murillo-Franco,
  • Matheus Costa Monteiro Santos,
  • Debora Danielle Virginio Silva,
  • Kelly Johana Dussán

摘要

The coffee industry generates approximately 6 million tons of waste annually, primarily spent coffee grounds (SCGs), whose disposal in landfills poses environmental risks. Therefore, new valorization strategies must be implemented to mitigate their environmental impact. In this sense, the objective of this study was to characterize SCGs and to optimize the dilute sulfuric acid pretreatment process for extracting oligosaccharides (OS). Optimal extraction conditions were determined using response surface methodology (RSM) with a Box-Behnken (BB) 33 design that included five central points for improved accuracy. The factors evaluated were temperature (140–190 °C), solid/liquid (S/L) ratio (1:40–1:4 g/mL), reaction time (20–120 min), and sulfuric acid concentration (0–2% v/v). Hemicellulose was identified as the predominant component, consisting mainly of mannose. OS extraction yields varied from 1.65 to 22.40 g per 100 g dry SCGs, depending on the process conditions. The quadratic model yielded an R2 value of 0.91128, indicating that the S/L ratio was the most influential factor, while reaction time had no significant effect. The optimized conditions—S/L ratio of 1:40 (g/mL), reaction time of 20 min, and H₂SO₄ concentration of 1.43% v/v at 168.57 °C—were experimentally validated and showed a margin of error of less than 9%. MALDI-TOF–MS analysis revealed oligosaccharide structures composed of hexose and pentose chains with up to eight sugar units. This study advances the understanding of OS extraction from SCGs via dilute acid pretreatment and provides valuable insight into waste valorization through process optimization and engineering approaches.