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<p>Pineapple crowns (PIC), a lignocellulosic agro-industrial waste, hold promising potential as a sustainable feedstock for microbial biochemicals production. PIC is discarded on land posing environmental issues due to microbial spoilages and landfills. However, limited research has been conducted on the valorization of PIC. This study therefore established an optimized technological platform for efficiently producing <span>d</span>-(−)-lactic acid from PIC via fermentation by an engineered <i>Klebsiella oxytoca</i> KIS004-91T. Optimal alkaline pretreatment of PIC with 0.75 N NaOH achieved the highest solid recovery (37.8 ± 4.0%, w/w) and fermentable sugar content (62.5 ± 0.1%, w/w). Enzymatic hydrolysis of 20&#xa0;g/L pretreated PIC using 60 PCU crude cellulase/g at 50&#xa0;°C yielded 13.69 ± 0.36&#xa0;g/L total sugars with 89.77 ± 1.41% cellulose saccharification. In batch separate hydrolysis and fermentation (SHF), <span>d</span>-(−)-lactic acid at 45.69 ± 1.16&#xa0;g/L with yield and productivity of 0.81 ± 0.02&#xa0;g/g of 1.92 ± 0.35&#xa0;g/L/h was produced from 100&#xa0;g/L pretreated PIC. Though simultaneous saccharification and fermentation (SSF) using 75&#xa0;g/L pretreated PIC resulted in a lower concentration with a yield and productivity of 31.50 ± 1.97&#xa0;g/L, 0.70 ± 0.03&#xa0;g/g and 1.07 ± 0.03&#xa0;g/L/h. Implementation of a fed-batch SHF strategy significantly improved <span>d</span>-(−)-lactic acid production to 62.87 ± 0.42&#xa0;g/L, with yield and productivity of 0.96 ± 0.07&#xa0;g/g (96% theoretical maximum) and 1.31 ± 0.01&#xa0;g/L/h. The process produced high optical purity of <span>d</span>-(−)-lactic acid (99.5% ee) with minimal by-products of 2,3-butanediol and acetate (~ 3.5&#xa0;g/L) in a low-cost medium without rich nutrients supplementation. These findings highlight the feasibility of utilizing PIC as an alternative substrate for sustainable and cost-effective <span>d</span>-(−)-lactic acid production, supporting waste management and advanced development of a zero-waste biorefinery.</p>

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Agro-industrial valorization of pineapple crown for producing high optical purity of d-(−)-lactic acid near theoretical maximum yield with minimal by-products in low-cost medium by metabolically engineered Klebsiella oxytoca

  • 期刊论文

  • 发表日期：

    2025年8月15日

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  • Socheata Chou,
  • Chutchawan Phosriran,
  • Walainud Congthai,
  • Kanyarat Onsanoi,
  • Sirima Suvarnakuta Jantama,
  • Kuan-Chen Cheng,
  • Kaemwich Jantama

摘要

Pineapple crowns (PIC), a lignocellulosic agro-industrial waste, hold promising potential as a sustainable feedstock for microbial biochemicals production. PIC is discarded on land posing environmental issues due to microbial spoilages and landfills. However, limited research has been conducted on the valorization of PIC. This study therefore established an optimized technological platform for efficiently producing d-(−)-lactic acid from PIC via fermentation by an engineered Klebsiella oxytoca KIS004-91T. Optimal alkaline pretreatment of PIC with 0.75 N NaOH achieved the highest solid recovery (37.8 ± 4.0%, w/w) and fermentable sugar content (62.5 ± 0.1%, w/w). Enzymatic hydrolysis of 20 g/L pretreated PIC using 60 PCU crude cellulase/g at 50 °C yielded 13.69 ± 0.36 g/L total sugars with 89.77 ± 1.41% cellulose saccharification. In batch separate hydrolysis and fermentation (SHF), d-(−)-lactic acid at 45.69 ± 1.16 g/L with yield and productivity of 0.81 ± 0.02 g/g of 1.92 ± 0.35 g/L/h was produced from 100 g/L pretreated PIC. Though simultaneous saccharification and fermentation (SSF) using 75 g/L pretreated PIC resulted in a lower concentration with a yield and productivity of 31.50 ± 1.97 g/L, 0.70 ± 0.03 g/g and 1.07 ± 0.03 g/L/h. Implementation of a fed-batch SHF strategy significantly improved d-(−)-lactic acid production to 62.87 ± 0.42 g/L, with yield and productivity of 0.96 ± 0.07 g/g (96% theoretical maximum) and 1.31 ± 0.01 g/L/h. The process produced high optical purity of d-(−)-lactic acid (99.5% ee) with minimal by-products of 2,3-butanediol and acetate (~ 3.5 g/L) in a low-cost medium without rich nutrients supplementation. These findings highlight the feasibility of utilizing PIC as an alternative substrate for sustainable and cost-effective d-(−)-lactic acid production, supporting waste management and advanced development of a zero-waste biorefinery.