Shikha Dahiya

Acidogenic fermentation of food waste for volatile fatty acid production with co-generation of biohydrogen.

Fermentation experiments were designed to elucidate the functional role of the redox microenvironment on volatile fatty acid (VFA, short chain carboxylic acid) production and co-generation of biohydrogen (H2). Higher VFA productivity was observed at pH 10 operation (6.3g/l) followed by pH 9, pH 6, pH 5, pH 7, pH 8 and pH 11 (3.5 g/l). High degree of acidification, good system buffering capacity along with co-generation of higher H2 production from food waste was also noticed at alkaline condition. Experiments illustrated the role of initial pH on carboxylic acids synthesis. Alkaline redox conditions assist solubilization of carbohydrates, protein and fats and also suppress the growth of methanogens. Among the carboxylic acids, acetate fraction was higher at alkaline condition than corresponding neutral or acidic operations. Integrated process of VFA production from waste with co-generation of H2 can be considered as a green and sustainable platform for value-addition.

Regulation of acidogenic metabolism towards enhanced short chain fatty acid biosynthesis from waste: metagenomic profiling

Short chain carboxylic (volatile fatty) acid (VFA) production in mixed microbiomes is majorly limited by the prevalence of methanogenic bacteria and the availability of substrate from waste to the biocatalyst during the fermentation process. To enhance the VFA production from food waste, the present study evaluates a strategy for selective enrichment of the biocatalyst by exposing it to acid-shock, followed by operation under alkaline conditions (pH 10). A comprehensive system based analysis was carried out during the bio-based platform chemical synthesis from waste, in conjugation with microbial profiling and bio-electrochemical analysis. After the selective enrichment of the biocatalyst, enhanced VFA synthesis was conducted with pretreated biocatalyst (PT; 11.1 g L−1) and compared with untreated parent biocatalyst (UT; 6.1 g L−​1). In both systems biohydrogen was the co-product. Variations in the VFA profiles were documented with respect to the biocatalyst used, which influenced the degree of acidification (DOA – PT: 37% and UT: 11%). A high fraction of acetic acid (6.9 g L−1) was observed, followed by butyric acid (2.6 g L−1) and propionic acid (1.3 g L−1) in PT operation, contrary to the control system (acetic acid, 3.9 g L−1, butyric acid, 1.6 g L−1; propionic acid, 0.9 g L−1). Specifically, the PT system showed the biosynthesis of iso-valeric acid: 0.15 g L−1 (C5) and caproic acid: 1.9 g L−1 (C6), which indicates the possibility for chain-elongation through the selective enrichment of the microbial community. The PT system showed Epeak at −0.415 V on the cyclic voltammogram, which corresponds to the involvement of the redox couple, H+/H2, correlating with the enhanced acidogenic process, unlike UT. Tailoring of the parent inoculum (pretreatment) resulted in the enrichment and enhancement of the capabilities of the biocatalyst in secreting the redox mediators, which were not detected in the UT system. Acidogenic firmicutes (spore formers) and fatty acid producing bacteroides were enriched in the PT system along with saccharolytic and proteolytic bacteria (Bacillus cellulosilyticus (alkalophile), Soehngenia saccharolytica, etc.). The presence of Clostridium autoethanogenum and Propionibacterium freudenreichii in the PT system supports effective utilization of complex carbohydrates, facilitating acidification.

Waste Biorefinery: A New Paradigm for a Sustainable Bioelectro Economy.

A waste biorefinery is a means to valorize waste as a renewable feedstock to recover biobased materials and energy through sustainable biotechnology. This approach holistically integrates remediation and resource recovery. Here we discuss the various technologies employable to construct a waste biorefinery platform and its place in a biobased economy.

Food waste biorefinery: Sustainable strategy for circular bioeconomy

Enormous quantity of food waste (FW) is becoming a global concern. To address this persistent problem, sustainable interventions with green technologies are essential. FW can be used as potential feedstock in biological processes for the generation of various biobased products along with its remediation. Enabling bioprocesses like acidogenesis, fermentation, methanogenesis, solventogenesis, photosynthesis, oleaginous process, bio-electrogenesis, etc., that yields various products like biofuels, platform chemicals, bioelectricity, biomaterial, biofertilizers, animal feed, etc can be utilized for FW valorisation. Integrating these bioprocesses further enhances the process efficiency and resource recovery sustainably. Adapting biorefinery strategy with integrated approach can lead to the development of circular bioeconomy. The present review highlights the various enabling bioprocesses that can be employed for the generation of energy and various commodity chemicals in an integrated approach addressing sustainability. The waste biorefinery approach for FW needs optimization of the cascade of the individual bioprocesses for the transformation of linear economy to circular bioeconomy.

High rate biomethanation technology for solid waste management and rapid biogas production: an emphasis on reactor design parameters.

A high rate biomethanation digester was designed and fabricated to study its real field treatment efficiency and simultaneous biogas generation. The major design parameters like self mixing, delinking hydraulic retention time and solid retention time etc. were considered for efficient performance. It was operated with an organic loading rate (OLR) of 1.5kg/m(3)d(-1) with composite food waste for about one year. The maximum treatment efficiency achieved with respect to total solid (TS) reduction and volatile solids (VS) reduction was 94.5% and 89.7%, respectively. Annual mean biogas of about 0.16m(3)/kgVSd(-1) was observed with methane content varying from 56% to 60% (v/v). The high competence of high rate digester is attributed to its specific design features and intermittent mixing of the digester contents and also due to the hydrodynamic principles involved in its operation.

Waste derived bioeconomy in India: A perspective

Environmental and climatic change issues, population explosion, rapid urbanisation, depletion of fossil reserves, need for energy security, huge waste generation, etc. are some of the inherent issues associated with the fossil based linear economy which need greater attention. In this context, the world is gradually transforming from fossil-based economy to a sustainable circular bio-economy. The biogenic waste which is generated in enormous quanties in India can be considered as potential feedstock for structuring the bio-based economy. This communication depicts the need for developing waste derived bioeconomy in the Indian perspective. Waste is now being perceived as a resource with value and believed to supplement petroleum feedstock to a great extent if properly utilized. The necessity to introduce waste as the core element for the future economic models which also allows sustainable development is discussed. The review also establishes drivers for the bioeconomy and structures the waste derived bioeconomy in a sustainable format to address the futuristic needs, scope and opportunities envisaged in the business and economic realm. The enabling technologies/processes that can be applied for biogenic wastes valorisation are elaborated. Circularizing the economy in a waste biorefinery model for the production of biobased products including bioenergy is discussed.

Building a Bio-Based Economy Through Waste Remediation: Innovation Towards Sustainable Future

Abstract The pursuit of sustainable technologies has become the priority over the past few years due to the impact of the unprecedented increase in human population and its adverse effects on the environment. Increase in population leads to an increase in waste generation and resource depletion, forcing us to look for alternatives and more sustainable ways to live. In this situation an already existing concept of waste treatment should be explored with a different goal—waste valorization, in which waste is transformed to energy and useful products including chemicals and materials. In this the biological systems (microorganisms) play a significant and central role. In-depth understanding of the elements and structures of the complex biological systems and predicting their reaction to external factors can lead to the development of technologies that benefit humankind and the environment leading to a bio-based economy.The pursuit of sustainable technologies has become the priority over the past few years due to the impact of the unprecedented increase in human population and its adverse effects on the environment. Increase in population leads to an increase in waste generation and resource depletion, forcing us to look for alternatives and more sustainable ways to live. In this situation an already existing concept of waste treatment should be explored with a different goal—waste valorization, in which waste is transformed to energy and useful products including chemicals and materials. In this the biological systems (microorganisms) play a significant and central role. In-depth understanding of the elements and structures of the complex biological systems and predicting their reaction to external factors can lead to the development of technologies that benefit humankind and the environment leading to a bio-based economy.

Impact of selectively enriched microbial communities on long-term fermentative biohydrogen production

The effect of selectively enriched inoculum for biohydrogen production and shifts in microbial communities was observed using anaerobic sequencing batch reactor (AnSBR). Significantly, combined pretreatment using acid and iodopropane resulted 3 fold increase in H2 production (8.65mol/kgCODR) over untreated control (2.63mol/kgCODR). Pretreatment showed significant shifts in the microbial communities which are thus accounted for enhanced H2 production. The high-throughput pyrosequence analysis depicted shifts in phylum Firmicutes and Proteobacteria. In the case of Proteobacteria, there was an increase in Betaproteobacterial, decrease in Epsilonproteobacterial and compositional variation in Alphaproteobacterial species. The decreased OTU number after pretreatment indicate, reduction of undesirable microbial populations while favouring conditions for microbiome that are involved in acidogenic, acetogenic and H2 production.

Strategic Design of Synthetic Consortium with Embedded Wastewater Treatment Potential: Deciphering the Competence of Isolates from Diverse Microbiome

Microorganisms plays vital role in efficient biological treatment. Supplementation of external microorganisms with high degradation rates can enhance the process efficiency significantly. Potential strains were isolated from long term wastewater treating reactors and identified using phylogenetic analysis of 16S rRNA gene fragments with the nearest neighbours extracted during BLAST search. Later the study was designed in two phases which revealed interesting findings. Phase I evaluates the potential of isolated strains viz., Pseudomonas otitidis, Bacillus firmus, Bacillus subtilis and Bacillus circulans for their individual ability in terms of COD and nutrients removal. Bacillus circulans showed highest carbon (COD) removal (70%; 0.56 kg CODR/m3-day), while maximum nutrients removal (nitrate, 81%; phosphates, 90%) was observed with Bacillus subtilis. B. firmus showed maximum volatile fatty acid (VFA) production. Based on Phase I results, four synthetic consortia were designed in phase II with diverse combination of isolates and evaluated for its remediation efficiencies. Consortium 4 (P. otitidis, B. subtilis and B. firmus) illustrated higher treatment potential [COD, 86%; SDR (cum): 0.64 kg CODR/m3-day; Nitrates, 87%; Phosphates, 97%]. The exploitation of such explicit consortia can overcome the inefficiencies pre-existing with the biological wastewater treatment plants by acting as prospective candidates for bio-augmenting the native microflora. This communication illustrated development of the efficient consortia using lab isolated strains to improve the performance of wastewater treatment.