Application of methanol and sweet potato vine hydrolysate as enhancers of citric acid production by Aspergillus niger

Abstract

BackgroundAgricultural waste is as an alternative low-cost carbon source or beneficial additives which catch most people’s eyes. In addition, methanol and sweet potato vine hydrolysate (SVH) have been reported as the efficient enhancers of fermentation according to some reports. The objective of the present study was to confirm SVH as an efficient additive in CA production and explore the synergistic effects of methanol and SVH in fermentation reactions.ResultsThe optimal fermentation conditions resulted in a maximum citric acid concentration of 3.729 g/L. The final citric acid concentration under the optimized conditions was increased by 3.6-fold over the original conditions, 0.49-fold over the optimized conditions without methanol, and 1.8-fold over the optimized conditions in the absence of SVH. Kinetic analysis showed that Q p, Y p/s, and Y x/s in the optimized systems were significantly improved compared with those obtained in the absence of methanol or SVH. Further, scanning electron microscopy (SEM) revealed that methanol stress promoted the formation of conidiophores, while SVH could neutralize the effect and prolong Aspergillus niger vegetative growth. Cell viability analysis also showed that SVH might eliminate the harmful effects of methanol and enhance cell membrane integrity.ConclusionsSVH was a superior additive for organic acid fermentation, and the combination of methanol and SVH displayed a significant synergistic effect. The research provides a preliminary theoretical basis for SVH practical application in the fermentation industry.

Food waste as a source of value‐added chemicals and materials: a biorefinery perspective

“…China is the country behind the highest share of CA production, whereas the companies that lead the CA sector are as follows: Archer Daniels Midland, Cargill, COFCO Biochemical (Anhui), Gadot Biochemical Industries and Jungbunzlauer Suisse. This titre is relatively low, however, if compared to the common values achieved using sucrose, molasses or corn hydrolysate (between 90 and 100 g L À1 in 6-7 days), but it is considerably better than that obtained with agro-based waste raw materials like apple pomace and peanut shell in a half to half ratio, where up to 2.6 g L À1 of CA was obtained using a co-culture of Aspergillus ornatus and Alternaria alternata growing at 30°C and pH 5.0 (Yu et al, 2017a). However, FW can even reduce the cost of raw materials, and processes have been studied at laboratory scale to such end (Kosseva, 2013).…”

“…In the last years, as a novel carbon source, waste cooking oil (WCO) has been utilised together with Yarrowia lipolytica SWJ-1b, a yeast, to obtain, after media optimisation, up to 31.7 g L À1 of CA (0.4 g/g of WCO) and 6.5 g L À1 of isocitric acid in 14 days, with minor titres of biooil (42.1 g per 100 g biomass/5.9 g biomass per litre). This titre is relatively low, however, if compared to the common values achieved using sucrose, molasses or corn hydrolysate (between 90 and 100 g L À1 in 6-7 days), but it is considerably better than that obtained with agro-based waste raw materials like apple pomace and peanut shell in a half to half ratio, where up to 2.6 g L À1 of CA was obtained using a co-culture of Aspergillus ornatus and Alternaria alternata growing at 30°C and pH 5.0 (Yu et al, 2017a).…”

“…Although the yield from FW to HMF was only 4.7% w/w, some preliminary calculations indicated in the economic feasibility of the process (Parshetti et al, 2015). The works of Yu et al, in 2016Yu et al, in and 2017aYu et al, in , 2017bYu et al, in , 2017c were centred on the transformation of FW on HMF in successive and one-pot processes, respectively. In the 2016 paper, these authors studied the effect of the metal catalyst in the successive conversion pathway of FW to glucose (44-65% mass yield) and HMF (8-9.5% mass yield), using SnCl 4 as catalyst.…”

The grand challenge of water, waste, wastewater and emissions engineering and valorization

“…Studies have also been performed on the direct production of other biofuels, e.g., waste bioconversion to bioethanol (Bibra et al, 2023) or thermochemical waste conversion processes for energy recovery (Kassim et al, 2022). Numerous other non-energy-related bioproducts have been obtained from organic waste as well, e.g., antioxidants (Kaur et al, 2019), lactic acid (Wang et al, 2016), citric acid (Yu et al, 2017), to mention only few.…”