High-level production of pullulan and its biosynthesis regulation in Aureobasidium pullulans BL06

Abstract

Pullulan has many potential applications in the food, pharmaceutical, cosmetic and environmental industries. However, the yield and molecular properties of pullulan produced by various strains still need to be promoted to fit the application needs. A novel yeast-like strain Aureobasidium pullulans BL06 producing high molecular weight (Mw) pullulan (3.3 × 106 Da) was isolated and identified in this study. The remarkable Mw of pullulan produced by A. pullulans BL06 was the highest level ever reported thus far. To further regulate the biosynthesis of pullulan in A. pullulans BL06, three gene knockout strains A. pullulans BL06 ΔPMAs, A. pullulans BL06 Δmel, and A. pullulans BL06 ΔPMAsΔmel, were constructed. The results showed that A. pullulans BL06 ΔPMAs could produce 140.2 g/L of moderate Mw (1.3 × 105 Da) pullulan after 120 h of fermentation. The highest yield level of pullulan to date could vastly reduce its production cost and expand its application scope and potential. The application experiments in food preservation showed that the moderate-Mw pullulan obtained in this work could reduce the weight loss of celery cabbages and mangos by 12.5% and 22%, respectively. Thus, the novel strains A. pullulans BL06 and A. pullulans BL06 ΔPMAs possessed unlimited development prospects in pullulan production at various Mw ranges and pullulan applications in multiple fields.

Hyper-Production of Pullulan by a Novel Fungus of Aureobasidium melanogenum ZH27 through Batch Fermentation

“…The pullulan yield (0.77 g/g) of strain ZH27 using sucrose was close to the reported one (~0.80 g/g) from high pullulan-producing wild-type A. melanogenum strains [ 13 , 18 ]. As for the productivity (0.87 g/L/h), it achieved a high level via batch fermentation among the wild-type strains, even though it was lower than those from fed-batch fermentation or some mutants [ 10 , 11 , 13 , 14 ]. Notably, the lower supernatant viscosity under the OC might result from high expressions of some enzymes (e.g., α-amylase and pullulanase) that hydrolyze pullulan ( Table 2 ), just as reported by a previous study [ 38 ].…”

“…Then, fresh cells harvested in the abovementioned liquid YPD medium were used to extract the genomic DNA using a Fungi Genomic DNA Extraction Kit (Solarbio, Beijing, China). To confirm the phylogenetic relationship between the target strain and other identified strains, the ITS sequence was amplified using primers ITS1 and ITS4, and sequenced [ 11 ]. A phylogenetic tree was accordingly constructed using MEGA 7.0 software (University of Kent, Canterbury, UK).…”

“…The strains are multicellular fungi encompassing yeast-like cells, swollen cells, conidia, chlamydospores, and mycelia types that thrive in diverse habitats, such as soils, plant leaves, oceans, and extreme environments [ 7 , 8 , 9 ]. Among the species of Aureobasidium , A. pullulans and A. melanogenum emerge as the most robust pullulan producers [ 1 , 10 , 11 ]. However, most wild-type strains yield less than 78 g/L of pullulan [ 2 , 3 , 8 , 12 ].…”

Pullulan Production from Sugarcane Bagasse Hemicellulosic Hydrolysate by Aureobasidium pullulans ATCC 42023 inBubble Column Reactor

“…Among biopolymers, pullulan has been mainly considered for its specific physicochemical and biological properties. It is a water-soluble homopolysaccharide that can be produced by fungi from renewable sources [1,2]. It is a non-hygroscopic, Fermentation 2024, 10, 322 2 of 14 biodegradable, and biocompatible polymer composed of maltotriose units (three glucose units linked by α-(1→4) glycosidic bonds) linked by α-(1→6) glycosidic bonds [2][3][4].…”

“…It is mainly used in the pharmaceutical (stabilizers, emulsifiers, gelling agents, water-binding agents, controlled release of drugs, and 3D/4Dprinting), chemical (coating, packaging, as sizing agent), and agri-food (starch substitute) industrial sectors [5,6]. In addition, pullulan has been recognized as a material of interest in tissue engineering [2]. This biopolymer is produced industrially under specific conditions through starch fermentation using wild strains of Aureobasidium pullulans, which are non-pathogenic and non-toxigenic microorganisms [7].…”