Prospects on bio-based 2,3-butanediol and acetoin production: Recent progress and advances.

The bio-based platform chemicals 2,3-butanediol (BDO) and acetoin have various applications in chemical, cosmetics, food, agriculture, and pharmaceutical industries, whereas the derivatives of BDO could be used as fuel additives, polymer and synthetic rubber production. This review summarizes the novel technological developments in adapting genetic and metabolic engineering strategies for selection and construction of chassis strains for BDO and acetoin production. The valorization of renewable feedstocks and bioprocess development for the upstream and downstream stages of bio-based BDO and acetoin production are discussed. The techno-economic aspects evaluating the viability and industrial potential of bio-based BDO production are presented. The commercialization of bio-based BDO and acetoin production requires the utilization of crude renewable resources, the chassis strains with high fermentation production efficiencies and development of sustainable purification or conversion technologies.

Synthesis of C2-C4 diols from bioresources: Pathways and metabolic intervention strategies.

Diols are important platform chemicals with extensive industrial applications in biopolymer synthesis, cosmetics, and fuels. The increased dependence on non-renewable sources to meet the energy requirement of the population raised issues regarding fossil fuel depletion and environmental impacts. The utilization of biological methods for the synthesis of diols by utilizing renewable resources such as glycerol and agro-residual wastes gained attention worldwide because of its advantages. Among these, biotransformation of 1,3-propanediol (1,3-PDO) and 2,3-butanediol (2,3-BDO) were extensively studied and at present, these diols are produced commercially in large scale with high yield. Many important isomers of C2-C4 diols lack natural synthetic pathways and development of chassis strains for the synthesis can be accomplished by adopting synthetic biology approaches. This current review depicts an overall idea about the pathways involved in C2-C4 diol production, metabolic intervention strategies and technologies in recent years.

Lignocellulose in future biorefineries: Strategies for cost-effective production of biomaterials and bioenergy.

Lignocellulosic biomass has been emerging as a biorefinery precursor for variety of biofuels, platform chemicals and biomaterials because of its specific surface morphology, exceptional physical, chemical and biological characteristics. The selection of proper raw materials, integration of nano biotechnological aspects, and designing of viable processes are important to attain a cost-effective route for the development of valuable end products. Lignocellulose-based materials can prove to be outstanding in terms of techno-economic viability, as well as being environmentally friendly and reducing effluent load. This review should facilitate the identification of better lignocellulosic sources, advanced pretreatments, and production of value-added products in order to boost the future industries in a cleaner and safer way.

Molecular biology interventions for activity improvement and production of industrial enzymes.

Metagenomics and directed evolution technology have brought a revolution in search of novel enzymes from extreme environment and improvement of existing enzymes and tuning them towards certain desired properties. Using advanced tools of molecular biology i.e. next generation sequencing, site directed mutagenesis, fusion protein, surface display, etc. now researchers can engineer enzymes for improved activity, stability, and substrate specificity to meet the industrial demand. Although many enzymatic processes have been developed up to industrial scale, still there is a need to overcome limitations of maintaining activity during the catalytic process. In this article recent developments in enzymes industrial applications and advancements in metabolic engineering approaches to improve enzymes efficacy and production are reviewed.

Recent advances in microbial biosynthesis of C3 - C5 diols: Genetics and process engineering approaches.

Diols derived from renewable feedstocks have significant commercial interest in polymer, pharmaceutical, cosmetics, flavors and fragrances, food and feed industries. In C3-C5 diols biological processes of 1,3-propanediol, 1,2-propanediol and 2,3-butanediol have been commercialized as other isomers are non-natural metabolites and lack natural biosynthetic pathways. However, the developments in the field of systems and synthetic biology paved a new path to learn, build, construct, and test for efficient chassis strains. The current review addresses the recent advancements in metabolic engineering, construction of novel pathways, process developments aimed at enhancing in production of C3-C5 diols. The requisites on developing an efficient and sustainable commercial bioprocess for C3-C5 diols were also discussed.

Genomics of Lactic Acid Bacteria for Glycerol Dissimilation.

Lactic acid bacteria (LAB) are functional starter cultures in food and dairy industry and are also regarded as power houses for bioprocess and fermentation technology. Due to extensive applications in food and medical applications, intensive research and developmental activities are going on throughout the world to understand the genomic and metabolic aspects during the past few decades. These LAB strains have significant role in production of value added chemicals and fuels from lignocellulosic biomass and other by-product streams establishing a circular bioeconomy. In this context, we discuss the physiology and genetics of crude glycerol dissimilation in lactic acid bacteria, the value added chemicals produced from biodiesel-derived crude glycerol. The overview of metabolic engineering strategies to improve the cellular traits and future perspectives in constructing cellulolytic/hemicellulolytic LAB strains to establish a renewable and sustainable cost-effective biorefinery is discussed.

An efficient aqueous two phase systems using dual inorganic electrolytes to separate 1,3-propanediol from the fermented broth.

An aqueous two phase extraction using K2CO3:K2HPO4/Isoproponal was investigated for the recovery of 1,3-propanediol from the fermented broth. Initially, the concentration of K2CO3 on phase formation, the partition co-efficient and recovery of 1,3-PDO was evaluated with a optimum salt concentration of 60%. Later the partition co-efficient was improved using dual inorganic salts, K2CO3 and K2HPO4 with an optimum concentration of 45% and 15% respectively. Using Central Composite Design, pH and temperature on partition and recovery of 1,3-PDO was evaluated. With the optimized physical conditions and inorganic salts concentration, ATPS extraction was carried out in synthetic solution as well as fermented broth resulting in maximum 1,3-PDO partition co-efficient value of 42.46 and 56.93 and recovery yield of 97.69 and 98.27% respectively. A fair partition was observed with organic acids and 1,3-PDO, with removal of lactic acid and acetic acid up to 93.29 and 90.42% respectively.

Self-cycling fermentation for 1,3-propanediol production: Comparative evaluation of metabolite flux in cell recycling, simple batch and continuous processes using Lactobacillus brevis N1E9.3.3 strain.

The microbial conversion of biodiesel derived crude glycerol to 1,3-propanediol (1,3-PDO) has attained high industrial value due to the broad range of applications as a monomer (1,3-PDO) in textile, cosmetic and polymer industries. This fine chemical through biological production addressed several limitations of the chemical process like high temperatures, pressure and expensive catalysts. In this study 1,3-propanediol production was achieved from a non-pathogenic lactic acid bacterial strain Lactobacillus brevis N1E9.3.3 in suspended and immobilized form under batch, sequential batch and continuous modes of fermentation. The microorganism was immobilized in polyurethane foam cubes. The effects of initial glycerol concentration on suspended and immobilized cells were investigated in stirred tank reactor. The maximum 1,3-PDO titers of 51.5g1,3-PDO/l and 42.59g1,3-PDO/l with a yield of 0.64g1.3-PDO/gGlycerol and 0.53g1.3-PDO/gGlycerol using suspended and immobilized cells respectively was observed in batch fermentation with an initial glycerol concentration of 80g/l. In repeated batch (self-cycling) fermentation 78.3g/l 1,3-PDO with 0.65g1.3-PDO/gGlycerol yield and 0.65g/l/h productivity was observed at the end of 5th cycle. A constant yield between 0.3-0.65g1.3-PDO/gGlycerol was observed with cell recycling using suspended and immobilized cells. The highest productivity of 1.735g1,3-PDO/l/h was observed in chemostat with immobilized cells.

Recent advances in the production of value added chemicals and lipids utilizing biodiesel industry generated crude glycerol as a substrate - Metabolic aspects, challenges and possibilities: An overview.

One of the major ecological concerns associated with biodiesel production is the generation of waste/crude glycerol during the trans-esterification process. Purification of this crude glycerol is not economically viable. In this context, the development of an efficient and economically viable strategy would be biotransformation reactions converting the biodiesel derived crude glycerol into value added chemicals. Hence the process ensures the sustainability and waste management in biodiesel industry, paving a path to integrated biorefineries. This review addresses a waste to wealth approach for utilization of crude glycerol in the production of value added chemicals, current trends, challenges, future perspectives, metabolic approaches and the genetic tools developed for the improved synthesis over wild type microorganisms were described.

Water hyacinth a potential source for value addition: An overview.

Water hyacinth a fresh water aquatic plant is considered as a noxious weed in many parts of the world since it grows very fast and depletes nutrients and oxygen from water bodies adversely affecting the growth of both plants and animals. Hence conversion of this problematic weed to value added chemicals and fuels helps in the self-sustainability especially for developing countries. The present review discusses the various value added products and fuels which can be produced from water hyacinth, the recent research and developmental activities on the bioconversion of water hyacinth for the production of fuels and value added products as well as its possibilities and challenges in commercialization.

Biological valorization of pure and crude glycerol into 1,3-propanediol using a novel isolate Lactobacillus brevis N1E9.3.3.

The aim of the study was to evaluate a novel onsite enrichment approach to isolate a crude glycerol utilizing facultative anaerobic bacteria. An onsite enrichment in natural conditions resulted an isolate, Lactobacillus brevis N1E9.3.3, that can utilize glycerol and produce 1,3-propanediol with a yield of 0.89g1,3-PDO/gGlycerol and productivity of 0.78g1,3-PDO/l/h at pH-8.5 under anaerobic conditions. Batch fermentation experiments with glycerol-glucose co-fermentation strategy was carried out to evaluate the production of 1,3-propanediol and other byproducts. The effect of other carbon sources as co-substrate was also evaluated. At the optimized condition, 18.6g/l 1,3-propanediol was monitored when biodiesel industry generated crude glycerol and 2.5% glucose were used as the substrate.