Evaluation of hydrolyzed cheese whey medium for enhanced bacterial cellulose production by Komagataeibacter rhaeticus MSCL 1463.

Industrial production of bacterial cellulose (BC) remains challenging due to significant production costs, including the choice of appropriate growth media. This research focuses on optimization of cheese whey (CW) based media for enhanced production of BC. Two modifications were made for CW medium for BC production with Komagataeibacter rhaeticus MSCL 1463. BC production in a medium of enzymatically hydrolyzed CW (final concentration of monosaccharides: glucose 0.13 g L-1, galactose 1.24 g L-1) was significantly enhanced, achieving a yield of 4.95 ± 0.25 g L-1, which markedly surpasses the yields obtained with the standard Hestrin-Schramm (HS) medium containing 20 g L-1 glucose and acid-hydrolyzed CW (final concentration of monosaccharides: glucose 1.15 g L-1, galactose 2.01 g L-1), which yielded 3.29 ± 0.12 g L-1 and 1.01 ± 0.14 g L-1, respectively. We explored the synergistic effects of combining CW with various agricultural by-products (corn steep liquor (CSL), apple juice, and sugar beet molasses). Notably, the supplementation with 15% corn steep liquor significantly enhanced BC productivity, achieving 6.97 ± 0.17 g L-1. A comprehensive analysis of the BC's physical and mechanical properties indicated significant alterations in fiber diameter (62-167 nm), crystallinity index (71.1-85.9%), and specific strength (35-82 MPa × cm3 g-1), as well as changes in the density (1.1-1.4 g cm-3). Hydrolyzed CW medium supplemented by CSL could be used for effective production of BC.

Microalgal conversion of whey and lactose containing substrates: current state and challenges.

Currently dairy processing by-products, such as whey, still propose a significant threat to the environment if unproperly disposed. Microalgal bioconversion of such lactose containing substrates can be used for production of valuable microalgae-derived bio-products as well as for significant reduction of environmental risks. Moreover, it could significantly reduce microalgae biomass production costs, being a significant obstacle in commercialization of many microalgae species. This review summarizes current knowledge on the use of lactose containing substrates, e.g. whey, for the production of value-added products by microalgae, including information on producer cultures, fermentation methods and cultivation conditions, bioprocess productivity and ability of microalgal cultures to produce ß-galactosidases. It can be stated, that despite several limitations lactose-containing substrates can be successfully used for both-the production of microalgal biomass and removal of high amounts of excess nutrients from the cultivation media. Moreover, co-cultivation of microalgae and other microorganisms can further increase the removal of nutrients and the production of biomass. Further investigations on lactose metabolism by microalgae, selection of suitable strains and optimisation of the cultivation process is required in order to enable large-scale microalgae production on these substrates.

Synthesis of bacterial cellulose by Komagataeibacter rhaeticus MSCL 1463 on whey.

Production costs of bacterial cellulose (BC) can be reduced using alternative fermentation media, e. g., various agricultural by-products including whey. This study focuses on whey as an alternative growth medium for BC production by Komagataeibacter rhaeticus MSCL 1463. It was shown that the highest BC production on whey was 1.95 ± 0.15 g/L, which is approximately 40-50% lower that BC production on standard HS media with glucose. It was also confirmed that K. rhaeticus MSCL 1463 can utilise both lactose and galactose as the sole C source in the modified HS medium. Different whey pre-treatment methods showed that the highest BC synthesis with K. rhaeticus MSCL 1463 was achieved in undiluted whey after standard pre-treatment procedure. Moreover, BC yield from substrate on whey was significantly higher (34.33 ± 1.21%) compared to the HS medium (16.56 ± 0.64%), which shows that whey can be used as a potential fermentation medium for BC production.

Bacterial cellulose production by Novacetimonas hansenii MSCL 1646 on apple juice.

Biomaterials and biopolymers, such as bacterial cellulose (BC), are becoming increasingly important as sustainable materials with a wide range of potential applications. However, BC industrial production is associated with several difficulties such as low BC production yields and high production costs; therefore, cheap alternative growth media, e.g. apple juice are being studied intensively. The aim of this study is to evaluate BC synthesis under static conditions on apple juice medium (AJM). The optimal concentration of apple juice in unsupplemented AJM for Novacetimonas hansenii MSCL 1646 was shown by its dilution 1:6 with water, which resulted in 0.89 ± 0.01 g/L of dry BC weight after 10 cultivation days. Low BC synthesis can be associated with insufficient N concentration in apple juice; therefore, different organic and inorganic N sources were evaluated in combination with AJM, and beef extract (5 g/L) was found to be the most suitable. Further, AJM optimisation experiment showed the optimal apple juice and beef extract concentrations as 1:2 and 15 g/L respectively, which resulted in 17.27 ± 0.07 g/L of dry BC weight, which is significantly higher than in standard Hestrin-Schramm (HS) medium (4.07 ± 0.02 g/L). Analysis of mechanical and physical properties showed that use of AJM results in changes in BC properties compared with the standard HS medium. Results of the study indicate that apple juice is an effective and cheap C source that in combination with appropriate N source leads to high BC synthesis and makes it suitable for industrial BC production. KEY POINTS: • Low quality apples can be used as raw material for BC production; • Beef extract improves BC synthesis in apple juice medium; • Use of apple juice and beef extract affect mechanical properties of BC.

Production of bacterial cellulose from glycerol: the current state and perspectives.

Current research in industrial microbiology and biotechnology focuses on the production of biodegradable microbial polymers as an environmentally friendly alternative to the still dominant fossil hydrocarbon-based plastics. Bacterial cellulose (BC) is important among microbial polymers due to its valuable properties and broad applications in variety of fields from medical to industrial technologies. However, the increase in BC production and its wider deployment is still limited by high costs of traditionally used raw materials. It is therefore necessary to focus on less expensive inputs, such as agricultural and industrial by-products or waste including the more extended use of glycerol. It is the environmentally harmful by-product of biofuel production and reducing it will also reduce the risk of environmental pollution. The experimental data obtained so far confirm that glycerol can be used as the renewable carbon source to produce BC through more efficient and environmentally friendly bioprocesses. This review summarizes current knowledge on the use of glycerol for the production of commercially prospective BC, including information on producer cultures, fermentation modes and methods used, nutrient medium composition, cultivation conditions, and bioprocess productivity. Data on the use of some related sugar alcohols, such as mannitol, arabitol, xylitol, for the microbial synthesis of cellulose are also considered, as well as the main methods and applications of glycerol pre-treatment briefly described.

Extracellular polysaccharides produced by bacteria of the Leuconostoc genus.

Structurally diverse biopolymers, including extracellular polysaccharides (EPS), synthesized by bacteria can possess physicochemical and functional properties that make them important products of microbial synthesis with a broad and versatile biotechnological potential. Leuconostoc spp. belongs to the group of lactic acid bacteria as one of the predominant members and are relevant not only in varied food fermentations, but also can be employed in the production of extracellular homopolysaccharides (HoPS) such as α-glucans (dextran, alternan) and ß-fructans (levan,inulin) from the sucrose-containing substrates. EPS are synthesized by specific Leuconostoc spp. extracellular glycosyltransferases [dextran sucrase, alternansucrase (ASR)] and fructosyltransferases (levansucrase, inulosucrase) and enzymatic reactions can be performed in whole culture systems as well as using cell-free enzymes. Both α-glucans and ß-fructans have a wide range of properties, mostly depending on their pattern of linkages, which, although differing in some respects, make suitable prerequisites for their versatile application in many fields, especially in the food industry and biomedicine. As a rule, these properties (polymer type, molecular mass, rheological parameters), as well as the overall EPS yield, are strain-specific for the selected producers and depend to a large extent on the nutritional and growth conditions used, which in many cases remain not sufficiently optimized for Leuconostoc spp. This review summarizes the current knowledge on the potential of Leuconostoc spp. to produce commercially relevant EPS, including information on their applications in various fields, producer strains, production methods and techniques used, selected conditions, the productivity of bioprocesses as well as the possible use of renewable resources for their development.

Production of bacterial cellulose from whey-current state and prospects.

Bacterial cellulose (BC) is a biopolymer with a wide range of potential applications starting from the food industry and biomedicine to electronics and cosmetics. Despite that, BC industrial production to date still is associated with certain difficulties. One of them is the high cost of growth media, which can reach up to 30% of production costs. To decrease production costs, use of industrial and agricultural by-products, including whey, as alternative growth media has been reported. Whey, as the main high-volume by-product of dairy industry, which is known for its low valorisation opportunities and negative environmental impact, can nevertheless be considered as an alternative growth medium for BC production. To date, several studies aimed at evaluating BC production on whey and lactose substrates have been reported, but they are still insufficient. Reviews of them showed that, in general, BC production on untreated whey- and lactose-containing media was lower than that on the standard medium. However, some wild and recombinant strains have been reported to produce BC on whey as good as the standard medium. Enzymatic and acidic pre-treatment of whey significantly enhanced BC yield. Changes in the microstructure of BC obtained from whey were also recognised, which should be considered regarding the impact on physical properties of the desired BC product. This mini-review indicates that currently whey can be recognised as quite a problematic alternative growth substrate for industrial BC production; however, further extensive studies may improve the prospects in both the search for a cheap alternative growth substrate for industrial BC production and valorisation of whey. KEY POINTS: • Whey is a by-product in which valorisation is still challenging. • Whey can be used for bacterial cellulose (BC) production. • BC yield and properties vary upon cultivation conditions and producer strains.