Jiming Xu

Erythritol production by Yarrowia lipolytica mutant strain M53 generated through atmospheric and room temperature plasma mutagenesis

Mutants of Yarrowia lipolytica with high erythritol production were generated through an atmospheric and room temperature plasma (ARTP) mutation system. Among these mutants, Y. lipolytica M53 exhibited the highest erythritol yield. In a batch culture, M53 produced 64.8xa0g/L erythritol from 100xa0g/L glycerol. The yields of byproducts (e.g. mannitol, arabitol, and α-ketoglutaric acid) were low, and the mechanisms underlying these changes were examined by measuring enzyme activities in the pentose phosphate pathway. Up to 145.2xa0g/L erythritol was produced by M53 from 200xa0g/L of glycerol, and erythritol accumulation was promoted by 3.7xa0mg/L of Cu2+, 10.15xa0mg/L of Mn2+, and 30.37xa0g/L of NaCl. Fed-batch cultivation of M53 in a 5-L fermentor produced 169.3xa0g/L erythritol with low levels of byproducts within 168xa0h. This finding confirmed the potential of M53 as an erythritol producer on a commercial scale.

Production of poly(β-l-malic acid) by Aureobasidium pullulans HA-4D under solid-state fermentation

Poly(β-l-malic acid) (PMA) production by Aureobasidium pullulans HA-4D was carried out through solid-state fermentation (SSF) using agro-industrial residues. Maximum PMA production (75.4mg/g substrate) was obtained from a mixed substrate of sweet potato residue and wheat bran (1:1, w/w) supplemented with NaNO3 (0.8%, w/w) and CaCO3 (2%, w/w), with an initial moisture content of 70% and inoculum size of 13% (v/w) for 8days. Repeated-batch SSF was successfully conducted for 5 cycles with a high productivity. The scanning electron microscopy showed that the yeast-like cells of A. pullulans HA-4D could grow well on the solid substrate surface. Moreover, the cost analysis showed that the unit price of PMA in SSF was much lower than that of SmF. This is the first report on PMA production via SSF, and this study provided a new method to produce PMA from inexpensive agro-industrial residues.

Synergistic effects of metal salt and ionic liquid on the pretreatment of sugarcane bagasse for enhanced enzymatic hydrolysis

High cost of ionic liquids (ILs) restricts the industrial application of IL-mediated lignocellulose pretreatment. In this study, a simple and economic technology for the pretreatment of natural lignocellulose was developed. The delignification capacity of aqueous choline ornithine ([Cho][Orn]) and hemicellulose-removal capacity of metal salt FeCl2 were combined. The changes of morphological structure and composition indicated a synergistic interaction of [Cho][Orn] and FeCl2 in the pretreatment process. The delignification and hemicellulose-removal capacity of aqueous [Cho][Orn]50% solution was significantly improved in the presence of FeCl2 by 28% and 53%, respectively. The combination use of FeCl2 and [Cho][Orn] made it possible to save the amount of IL used for pretreatment in half. Enhancement effect of metal salts on the IL-pretreatment efficiency was proved.

Economic co-production of poly(malic acid) and pullulan from Jerusalem artichoke tuber by Aureobasidium pullulans HA-4D

Backgroundpoly(L-malic acid) (PMA) is a water-soluble polyester with many attractive properties in medicine and food industries, but the high cost of PMA fermentation has restricted its further application for large-scale production. To overcome this problem, PMA production from Jerusalem artichoke tubers was successfully performed. Additionally, a valuable exopolysaccharide, pullulan, was co-produced with PMA by Aureobasidum pullulans HA-4D.ResultsThe Jerusalem artichoke medium for PMA and pullulan co-production contained only 100xa0g/L hydrolysate sugar, 30xa0g/L CaCO3 and 1xa0g/L NaNO3. Compared with the glucose medium, the Jerusalem artichoke medium resulted in a higher PMA concentration (114.4xa0g/L) and a lower pullulan concentration (14.3xa0g/L) in a 5xa0L bioreactor. Meanwhile, the activity of pyruvate carboxylase and malate dehydrogenas was significantly increased, while the activity of α-phosphoglucose mutase, UDP-glucose pyrophosphorylase and glucosyltransferase was not affected. To assay the economic-feasibility, large-scale production in a 1xa0t fermentor was performed, yielding 117.5xa0g/L PMA and 15.2xa0g/L pullulan.ConclusionsIn this study, an economical co-production system for PMA and pullulan from Jerusalem artichoke was developed. The medium for PMA and pullulan co-production was significantly simplified when Jerusalem artichoke tubers were used. With the simplified medium, PMA production was obviously stimulated, which would be associated with the improved activity of pyruvate carboxylase and malate dehydrogenas.

Effects of osmotic pressure and pH on citric acid and erythritol production from waste cooking oil by Yarrowia lipolytica

Erythritol and citric acid could be produced from waste cooking oil (WCO) by Yarrowia lipolytica under different medium conditions, and osmotic pressure together with pH were considered to be the critical factors in this process. High osmotic pressure (2.76 osmol/L) combined with low pH (pH 3.0) promoted the highest yield of erythritol (21.8 g/L) accompanied by low‐producing citric acid (2.5 g/L). By contrast, the highest citric acid biosynthesis (12.6 g/L) was detected under a pH of 6.0 and an osmotic pressure of 0.75 osmol/L, when only 4.0 g/L of erythritol was yielded. Moreover, lipase activities in these two media were also detected, and pH 3.0–OP 2.76 was supposed to be more beneficial to lipase activity. Biochemical pathways involved in the biosynthesis of erythritol and citric acid were subsequently investigated, and the products yielded from WCO were assumed to be correlated with the activities of transketolase, erythrose reductase, citrate synthase, and glycerol kinase. However, RT‐PCR analysis revealed that mRNA levels of these enzymes did not significantly differ, confirming that metabolic flux regulations of erythritol and citric acid mostly took place at the post‐transcriptional level.

Erythritol production by Yarrowia lipolytica from okara pretreated with the in-house enzyme pools of fungi

Okara (soybean residue) is an ideal erythritol feedstock due to its low price and high-nutrient content. Fungal-fermentations were carried out in okara using in-house enzyme pools generated by Mucor flavus or Trichoderma reesei to make okara more accessibility in the subsequent erythritol production using Yarrowia lipolytica. Mucor-fermented okara produced a high erythritol yield because of its special component and micromorphology. Five days is the optimal period for Mucor fermentation. Different fermentation modes were compared in terms of erythritol production and yield. The concentration of Mucor-fermented okara in erythritol fermentation medium was optimal at 30.0g/L. Moreover, 40.0g/L NaCl was added as the osmotic regulator. No extra ingredient was needed during this process. Results of 5-L fermentations showed that an erythritol titer of 14.7g/L, with a yield of 0.49g/g okara was obtained. These findings indicated that Mucor-fermented okara was an economically alternative feedstock for low-cost erythritol production.

Novel two-stage solid-state fermentation for erythritol production on okara–buckwheat husk medium

An economical model of two-stage solid state fermentation (SSF) (prefermentation stage with Mucor flavus and in situ erythritol fermentation stage with Yarrowia lipolytica) for enhancing erythritol production was investigated. Buckwheat husk (BH) was utilized as inert support for the first time and okara as the substrate. Morphological properties suggested yeast cells were exposed in adequate oxygen leading to high erythritol yield, and enzyme activities analysis indicated M. flavus and Y. lipolytica grew and cooperated well during the two ferment stages. Maximum erythritol production (143.3u202fmg/gds) was obtained from okara-BH mixture (5:2, w/w) supplemented with 0.01u202fg/gds NaCl, with an initial moisture content of 60% and pH of 4.0 for 192u202fh, while undesired mannitol and citric acid were suppressed. Compared with submerged fermentation, two-stage SSF was short period, energy conserving and operable for erythritol production from insoluble wastes, and this is the first report on erythritol production via SSF.