Elucidate biorefinery inhibition effect on commercially collected food waste and greener pre-treatment for sophorolipids production

Research output: Conference PapersRGC 31A - Invited conference paper (refereed items)Yespeer-review

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Original languageEnglish
Publication statusPublished - 1 Jun 2023

Conference

TitleInternational Conference on Solid Waste 2023 (ICSWHK2023): Waste Management in Circular Economy and Climate Resilience
LocationHong Kong Convention and Exhibition Centre
PlaceHong Kong
Period31 May - 3 June 2023

Abstract

Secondary or waste organic streams have been used to produce sophorolipids (SLs) in the prospective of circular economy, and food waste (FW) is recognized as a promising feedstock. However, the quality of FW varies according to the location and seasonal changes, thereby resulting in different inhibitor’s composition and interfere with the sustainable sophorolipids production. This study aimed to characterize the presence of inhibitors in a commercially collected FW, followed by designing a FW pre-treatment strategy to remove the inhibitors for sustainable sophorolipids (SLs) production. Key findings: Compare with the fresh canteen FW, the commercial FW hydrolysate had a low glucose concentration (29.40 ± 8.65 g L−1 versus 49.60 ± 2.97 g L−1), high fructose (9.73 ± 8.46 g L−1 versus 3.10 ± 0.14 g L−1), ethanol concentration (3.00 ± 2.62 g L−1 versus 2.55 ± 0.07 g L−1), lower pH (3.55 ± 0.10 versus 4.62 ± 0.12), and extra lactic acid and acetic acid of 32.10 ± 3.84 and 5.77 ± 0.21 g L−1, respectively. This was due to the facts that commercial FW was mixed and naturally fermented during collection and processing. SL bioprocess of the untreated commercial FW hydrolysate resulted in lower SL production was ascribed by low C/N ratio and inhibitory effect of lactic acid. A single factor inhibition experiment has proven a dose dependent inhibitory effect of lactic acid, at concentration relevant to the commercial FW hydrolysate (i.e., 40 g L-1), and a 98.7% and 46.7% drop in SLs and CDW observed. Further experiments indicated that increase in nitrogen concentration increased the CDW and partly improved SLs production regardless of the lactic acid concentration in the medium. To further reduce the inhibitory effect of commercially collected FW on SLs production, a washing step using deionized water was included in the pretreatment. Although, the washing of the FW resulted in a complete removal of lactic acid and partly reduced of acetic acid and ethanol, however the washing also led to the loss of 62% ± 1.72% free amino nitrogen (FAN), despite the residual FAN was still high enough to support for SLs bioprocess. Further SLs bioprocess of the pre-treated commercial FW hydrolysate increased the SLs titre to 115.3 ± 9.3 g L-1 which is 8.5-fold higher than that of the untreated counterpart (i.e.,13.5 ± 3.2 g L-1). Conclusions: This study identified lactic acid as the major inhibitor of commercially collected FW, and a cost-effective pre-treatment method. A high FAN containing fermentation method was also provided to overcome the inhibition issue. This work strongly enhanced the actual operability of FW-based biorefinery and significantly accelerated the establishment of a circular bioeconomy.

Research Area(s)

  • : Food waste inhibitor, Lactic acid, Sophorolipids, Starmerella bombicola, Sustainability

Citation Format(s)

Elucidate biorefinery inhibition effect on commercially collected food waste and greener pre-treatment for sophorolipids production. / To, M.H.; Wang, H.; Miao, Y. et al.
2023. International Conference on Solid Waste 2023 (ICSWHK2023): Waste Management in Circular Economy and Climate Resilience, Hong Kong.

Research output: Conference PapersRGC 31A - Invited conference paper (refereed items)Yespeer-review