Insights into Bacterial Cellulose Biosynthesis from Different Carbon Sources and the Associated Biochemical Transformation Pathways in Komagataeibacter sp. W1

Abstract

Cellulose is the most abundant and widely used biopolymer on earth and can be produced by both plants and micro-organisms. Among bacterial cellulose (BC)-producing bacteria, the strains in genus Komagataeibacter have attracted wide attention due to their particular ability in furthering BC production. Our previous study reported a new strain of genus Komagataeibacter from a vinegar factory. To evaluate its capacity for BC production from different carbon sources, the present study subjected the strain to media spiked with 2% acetate, ethanol, fructose, glucose, lactose, mannitol or sucrose. Then the BC productivity, BC characteristics and biochemical transformation pathways of various carbon sources were fully investigated. After 14 days of incubation, strain W1 produced 0.040⁻1.529 g L^-1 BC, the highest yield being observed in fructose. Unlike BC yields, the morphology and microfibrils of BCs from different carbon sources were similar, with an average diameter of 35⁻50 nm. X-ray diffraction analysis showed that all membranes produced from various carbon sources had 1⁻3 typical diffraction peaks, and the highest crystallinity (i.e., 90%) was found for BC produced from mannitol. Similarly, several typical spectra bands obtained by Fourier transform infrared spectroscopy were similar for the BCs produced from different carbon sources, as was the I_α fraction. The genome annotation and Kyoto Encyclopedia of Genes and Genomes analysis revealed that the biochemical transformation pathways associated with the utilization of and BC production from fructose, glucose, glycerol, and mannitol were found in strain W1, but this was not the case for other carbon sources. Our data provides suggestions for further investigations of strain W1 to produce BC by using low molecular weight sugars and gives clues to understand how this strain produces BC based on metabolic pathway analysis.

Keywords: Komagataeibacter; bacterial cellulose; carbon sources; genome sequencing; metabolic pathway.

Figure 1

Bacterial cellulose (BC) production by Komagataeibacter sp. W1 grown in media spiked with different carbon sources. (A) the raw samples, (B) the samples after pre-treatment with 0.1 M NaOH for 2 h and freeze-dried for 24 h and (C) the BC yields. Different letters in red indicate no significant difference between the setups according to Limited Slip Differential (LSD) test (p ≤ 0.05).

Figure 2

Morphology (A–H) and diameter distribution (a–h) of the BC produced by Komagataeibacter sp. W1 grown in the media spiked with different carbon sources. While the BC morphology was observed with scanning electron microscopy (SEM) with a spot of 3.0, high voltage of 15 KeV, and magnification of 20,000×, the diameter calculation was performed on Nano Measurer 1.2 by calculating 100 nanofibrils randomly on the SEM images.

Figure 3

Comparative X-ray diffraction (XRD) analysis of the BC produced by Komagataeibacter sp. W1 grown in the media spiked with various carbon sources. The XRD pattern was obtained using nickel filtered copper K_α radiation, with 0.1° steps, from 4° to 70° (2θ).

Figure 4

Comparative Fourier transform infrared (FTIR) analysis of the BC produced by Komagataeibacter sp. W1 grown in media spiked with various carbon sources. The analysis was conducted on a Nicolet iS5 in the Attenuated Total Reflectance (ATR) mode with 32 scans per measurement between 400 and 4000 cm⁻¹. The detailed information of peaks 1–22 is given in Table 3.

Figure 5

The number of orfs associated with carbon source metabolisms and BC biosynthesis and regulation. The orfs shown here were retrieved from the genes and corresponding protein annotation data. While the numbers on the top of the bars indicate the total number of predicted genes involved in carbon source metabolisms and BC biosynthesis and regulation, the ones below the line indicate the number of the genes that can be annotated to certain Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. It’s worthy to note that the description ‘others’ indicates the key metabolic intermediates during the transformation between glucose and glycerol or fructose and glycerol. More details can be found in Tables S1 and S2.

Figure 6

Schematic diagram of carbon metabolism and BC biosynthesis pathways in Komagataeibacter sp. W1. The comprehensive analysis was conducted by incorporating the key metabolic intermediates and associated enzymes responsible for carbon source transformation and BC biosynthesis in different KEGG pathways. The numbers in the figure are the Enzyme Commission number, while the red and black ones indicate the associated enzymes present and absent respectively in Komagataeibacter sp. W1. The asterisks indicate the enzymes absent in the labeled pathways but present in other pathways in our study, thus it is unknown whether they work in the labeled pathways. The question mark indicating whether the pathway is present, is unclear based on our data and remains for future investigations. More information of the enzymes and the associated genes and pathways (ko numbers) are listed in Table S2. P, phosphate; GDP, guanosine diphosphate; UDP, uridine diphosphate; PRPP, phosphoribosyl pyrophosphate; ThPP, thiamine diphosphate; TCA, tricarboxylic acid cycle; Acetyl-CoA, acetyl coenzyme A.