Comparative analysis of PHAs production by Bacillus megaterium OUAT 016 under submerged and solid-state fermentation

Synergistic approach for enhanced production of polyhydroxybutyrate by Bacillus pseudomycoides SAS-B1: Effective utilization of glycerol and acrylic acid through fed-batch fermentation and its environmental impact assessment

The continual rise in the consumption of petroleum-based synthetic polymers raised a significant environmental concern. Bacillus pseudomycoides SAS-B1 is a gram-positive rod-shaped halophilic bacterium capable of accumulating Polyhydroxybutyrate (PHB)-an intracellular biodegradable polymer. In the present study, the optimal conditions for cell cultivation in the seed media were developed. The optimal factors included a preservation age of 14 to 21 days (with 105 to 106 cells/mL), inoculum size of 0.1 % (w/v), 1 % (w/v) glucose, and growth temperature of 30 °C. The cells were then cultivated in a two-stage fermentation process utilizing glycerol and Corn Steep Liquor (CSL) as carbon and nitrogen sources, respectively. PHB yield was effectively increased from 2.01 to 9.21 g/L through intermittent feeding of glycerol and CSL, along with acrylic acid. FTIR, TGA, DSC, and XRD characterization studies were employed to enumerate the recovered PHB and determine its physicochemical properties. Additionally, the study assessed the cradle-to-gate Life Cycle Assessment (LCA) of PHB production, considering net CO2 generation and covering all major environmental impact categories. The production of 1000 kg of PHB resulted in lower stratospheric ozone depletion and comparatively reduced carbon dioxide emissions (2022.7 kg CO2 eq.) and terrestrial ecotoxicity (9.54 kg 1,4-DCB eq.) than typical petrochemical polymers.

Reclamation of chromium-contaminated soil by native Cr(VI)-reducing and PHA-accumulating Bacillus aryabhattai CTSI-07

Reclamation of chromium-contaminated soil by bacteria is a big confront concerning to soil health restoration, food safety, and environmental protection. Herein, the chromium-resistant Bacillus aryabhattai CTSI-07 (MG757377) showed resistance to 1000 and 300 ppm of Cr(VI) in nutrient rich Luria Bertani (LB) and nutrient-deficient sucrose low phosphate (SLP) medium, respectively. It reduced 96.7% of Cr(VI) from contaminated soil in the presence of 100 ppm of Mg within 96 h under optimized conditions. Furthermore, Cr(VI) reduction by the bacteria was validated by Fourier transform infrared spectroscopic (FTIR) and X-ray diffraction (XRD) analysis. Besides Cr(VI) reduction, the bacterial strain also showed plant growth promoting traits like N2 fixation and indole acetic acid (IAA) production. On the other hand, transmission electron microscopy (TEM) imaging confirmed polyhydroxyalkanoates' (PHAs) granule accumulation and 0.5 g/l of PHAs was extracted from bacterial cell using SLP medium. Infra-red (IR) spectra and proton nuclear magnetic resonance (1H NMR) chemical shift patterns established the PHAs as polyhydroxybutyrate (PHB). Melting (Tm) and thermal degradation (Td) temperature of the PHB were 169 °C and 275 °C, respectively, as evident from thermogravimetry differential thermal analysis (TG-DTA). Atomic force microscopic (AFM) imaging depicted that the PHB film surface was rough and regular. Furthermore, the multi-metal-resistant, plant growth-promoting, and PHB-producing bacteria could reduce 99.82% of Cr(VI) from contaminated soil within 120 days in pot culture. Thus, it can be used for long-term reclamation of chromium-contaminated soil to restore soil health, provide food safety, and environmental protection.

PHAs production by facultative anaerobic bacteria Bacillus cereus FM5 through submerged and solid-state fermentation under anoxic condition

PHAs (polyhydroxyalkanoates) are the bio-polyester synthesized by different aerobic and anaerobic bacteria as energy storage granule. However, its synthesis by anaerobes or facultative anaerobes is an imperative part of their physiology via assimilating broad range of substrates than aerobes. Thus, three Gram positive facultative anaerobic PHAs producers viz., Enterococcus sp. FM3, Actinomyces sp. CM4 and Bacillus sp. FM5 were selected. Among them, Bacillus sp. FM5 showed higher cell biomass production in MSM (mineral salt medium) comprised of glucose & peptone as carbon & nitrogen source at pH 9, temperature 37 °C, inoculum 10% and incubation period 72 h. Under optimized condition, Bacillus sp. FM5 produced 0.89 and 1.5 g l^-1 of PHAs through submerged and solid-state fermentation in anoxic condition. In-silico analysis confirmed the facultative anaerobic PHAs producing bacteria as Bacillus cereus FM5. IR spectra of PHAs illustrated a strong absorption peak at 1718.50 cm^-1 representing carbonyl ester (C=O) functional group of PHB (polyhydroxybutyrate), belonging to the family PHAs. It is the first report demonstrating PHAs production by Bacillus cereus FM5 in anoxic condition through different bioprocess technology, which may pave the way in the arena of further biopolymer research.

In-silico analysis of a halophilic bacterial isolate-Bacillus pseudomycoides SAS-B1 and its polyhydroxybutyrate production through fed-batch approach under differential salt conditions

Polyhydroxybutyrate (PHB) is a natural biopolymer and a viable substitute for petroleum-derived polymers that possess immense potential for diverse applications. In the present study, PHB was produced by a halophilic bacteria identified as Bacillus pseudomycoides SAS-B1 by 16S rRNA gene sequencing. The bacterial genome was evaluated through complete genome sequencing, which elucidated a 5,338,308 bp genome with 34.88 % of G + C content and 5660 genes. Other genome attributes were analyzed such as functional profiling, gene ontology, and metabolic pathways. Genes involved in PHB biochemical pathway were identified such as phaA, phaB, and phaC. Furthermore, sodium-dependent transporters and other ATP-binding genes were identified in the genome that may be involved in sodium uptake during saline conditions. The PHB production by B. pseudomycoides SAS-B1 was examined under differential salt conditions. The PHB yield was increased from 3.14 ± 0.02 g/L to 6.12 ± 0.04 g/L when salinity was increased upto 20 g/L with intermittent feeding of glucose and corn steep liquor. FTIR, NMR, and GC-MS studies elucidated the presence of desired functional groups, molecular structure, and monomeric compositions of PHB respectively. Further, TGA revealed the thermal stability of the recovered PHB upto (220-230) °C and has a crystallinity index of upto 33 ± 0.5 % as confirmed by XRD analysis.

Application of the solid-state fermentation process and its variations in PHA production: a review

Solid-state fermentation (SSF) is a type of fermentation process with potential to use agro-industrial by-products as a carbon source. Nonetheless, there are few studies evaluating SSF compared to submerged fermentation (SmF) to produce polyhydroxyalkanoates (PHAs). Different methodologies are available associating the two processes. In general, the studies employ a 1st step by SSF to hydrolyze the agro-industrial by-products used as a carbon source, and a 2nd step to produce PHA that can be carried out by SmF or SSF. This paper reviewed and compared the different methodologies described in the literature to assess their potential for use in PHA production. The studies evaluated showed that highest PHA yields (86.2% and 82.3%) were achieved by associating SSF and SmF by Cupriavidus necator. Meanwhile, in methodologies using only SSF, Bacillus produced the highest yields (62% and 56.8%). Since PHA (%) does not necessarily represent a higher production by biomass, the productivity parameter was also compared between studies. We observed that the highest productivity results did not necessarily represent the highest PHA (%). C. necator presented the highest PHA yields associating SSF and SmF, however, is not the most suitable microorganism for PHA production by SSF. Concomitant use of C. necator and Bacillus is suggested for future studies in SSF. Also, it discusses the lack of studies on the association of the two fermentation methodologies, and on the scaling of SSF process for PHA production. In addition to demonstrating the need for standardization of results, for comparison between different methodologies.

The Hyperproduction of Polyhydroxybutyrate Using Bacillus mycoides ICRI89 through Enzymatic Hydrolysis of Affordable Cardboard

Bioplastics are contemplated as remarkable substitutes for conventional plastics to accommodate green technological advancements. However, their industrial production has not been fully implemented owing to the cost of carbon resources. From another perspective, valorizing different paper mill wastes has become a prominent research topic. These materials may serve as an affording sustainable feedstock for bioplastic production. Adjustment of cardboard waste hydrolysate as suitable fermentation media for production of bacterial polyhydroxyalkanoates (PHAs) has been investigated. Cardboard samples were defibered and dried before enzymatic hydrolysis. The enzymatic degradation of commercial cellulase was monitored over 15 days. Interestingly, 18.2 ± 0.2 g/L glucose yield was obtained from 50 g cardboard samples using a 1.5% (v/v) enzyme concentration. The samples exhibited maximum weight loss values of 69-73%. Meanwhile, five soil samples were collected from local sites in Lodz, Poland. A total of 31 bacterial isolates were screened and cultured on Nile blue plates. Analysis of the 16S rRNA gene sequence of the most potent producer revealed 100% similarity to Bacillus mycoides. Cardboard hydrolysates whole medium, modified MSM with cardboard hydrolysate and nitrogen depleted MSM with cardboard hydrolysate were utilized for PHA production, followed by PHA productivity and cell dry weight (CDW) estimation compared to glucose as a standard carbon source. An impressive PHA accumulation of 56% CDW was attained when the waste hydrolysate was used as a carbon source. FTIR and NMR analysis of the isolated PHA indicated that functional groups of the polymer were related to PHB (polyhydroxybutyrate). Thermal analysis demonstrates that PHB and PHB-CB (PHB produced from cardboard hydrolysate) have degradation temperatures of 380 and 369 °C, respectively, which reflect the high thermal stability and heat resistance compared to the same properties for a standard polymer. This is the first demonstration of full saccharification of corrugated cardboard paper waste for high-level production of PHA. In addition, the attained PHB productivity is one of the highest levels achieved from a real lignocellulosic waste.

Environmental factors affecting the diversity of psychrophilic microbial community in the high altitude snow-fed lake Hemkund, India

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Seasonal variation among the physicochemical attributes of Hemkund Lake.

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Exploration of psychrophilic microbial diversity of high-altitude snow-fed Lake Hemkund.

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This lake is located at an altitude of 4170 m a.s.l. and is also an important tributary of Lakshman Ganga.

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Study of important physicochemical factors affecting the microbial diversity at various sampling sites.

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Importance of phychrophilic microbial diversity to the society.

The current examination incorporates the evaluation of limnological boundaries influencing the microbial diversity and its distribution in the Hemkund Lake, a high altitude aquatic body located at an elevation of 4,170 m a.s.l. in the Himalayan state Uttarakhand of India. Samples of water were collected for three continuous years (2018–2020) in three sampling attempts each year. Four water sampling sites were identified and studied across the lake during two years of the study periods. A total of nineteen physicochemical parameters of lake water were recorded. Few of the parameters were analyzed at the site whereas the leftover parameters were analyzed in the laboratory at the Department. The diversity of microorganisms was determined via morphological, biochemical, MALDI-TOF MS, and molecular approaches (16S and 18S rRNA sequencing). Environmental variables i.e., DO, BOD, total coliform, and TDS showed huge variation at site 2 among all the four water sampling sites. The water temperature of Hemkund Lake was observed from 4.9°C to 6.1°C whereas; dissolved oxygen was recorded from 6.0 to 8.2 mg.l⁻¹. The α-diversity of microorganisms in the Hemkund Lake was found to be nineteen with ten bacterial strains, four actinomycetes strains, and five fungal strains. Janthinobacterium lividum, Pseudomonas tolaasii, Pseudomonas rhodesiae, and Pseudomonas fluorescens are a few important and key species that were found in the lake water. The present study on the diversity of psychrophilic microorganisms in the high altitude Lake Hemkund could be a great reference for further research activities on comparable viewpoints in different parts of the Himalaya. This baseline information can also help the administrative officials to take necessary steps for its conservation and management.

Established and Emerging Producers of PHA: Redefining the Possibility

The polyhydroxyalkanoate was discovered almost around a century ago. Still, all the efforts to replace the traditional non-biodegradable plastic with much more environmentally friendly alternative are not enough. While the petroleum-based plastic is like a parasite, taking over the planet rapidly and without any feasible cure, its perennial presence has made the ocean a floating island of life-threatening debris and has flooded the landfills with toxic towering mountains. It demands for an immediate solution; most resembling answer would be the polyhydroxyalkanoates. The production cost is yet one of the significant challenges that various corporate is facing to replace the petroleum-based plastic. To deal with the economic constrain better strain, better practices, and a better market can be adopted for superior results. It demands for systems for polyhydroxyalkanoate production namely bacteria, yeast, microalgae, and transgenic plants. Solely strains affect more than 40% of overall production cost, playing a significant role in both upstream and downstream processes. The highly modifiable nature of the biopolymer provides the opportunity to replace the petroleum plastic in almost all sectors from food packaging to medical industry. The review will highlight the recent advancements and techno-economic analysis of current commercial models of polyhydroxyalkanoate production. Bio-compatibility and the biodegradability perks to be utilized highly efficient in the medical applications gives ample reason to tilt the scale in the favor of the polyhydroxyalkanoate as the new conventional and sustainable plastic.

Production of polyhydroxyalkanoates (PHAs) by Bacillus megaterium using food waste acidogenic fermentation-derived volatile fatty acids

High production costs still hamper fast expansion of commercial production of polyhydroxyalkanoates (PHAs). This problem is greatly related to the cultivation medium which accounts for up to 50% of the whole process costs. The aim of this research work was to evaluate the potential of using volatile fatty acids (VFAs), derived from acidogenic fermentation of food waste, as inexpensive carbon sources for the production of PHAs through bacterial cultivation. Bacillus megaterium could assimilate glucose, acetic acid, butyric acid, and caproic acid as single carbon sources in synthetic medium with maximum PHAs production yields of 9-11%, on a cell dry weight basis. Single carbon sources were then replaced by a mixture of synthetic VFAs and by a VFAs-rich stream from the acidogenic fermentation of food waste. After 72 h of cultivation, the VFAs were almost fully consumed by the bacterium in both media and PHAs production yields of 9-10%, on cell dry weight basis, were obtained. The usage of VFAs mixture was found to be beneficial for the bacterial growth that tackled the inhibition of propionic acid, iso-butyric acid, and valeric acid when these volatile fatty acids were used as single carbon sources. The extracted PHAs were revealed to be polyhydroxybutyrate (PHB) by characterization methods of Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The obtained results proved the possibility of using VFAs from acidogenic fermentation of food waste as a cheap substrate to reduce the cost of PHAs production.

Evaluation of Fed-Batch Fermentation for Production of Polyhydroxybutyrate With a Banana Pulp Juice Substrate From an Agro Industrial By-Product

Pollution resulting from the persistence of plastics in the environment has driven the development of substitutes for these materials through fermentation processes using agro-industrial wastes. Polyhydroxybutyrate (PHB) is a rapidly biodegradable material with chemical and mechanical properties comparable to those of some petroleum-derived plastics. PHB accumulates intracellularly as an energy reserve in a wide variety of microorganisms exposed to nutritionally imbalanced media. The objective of this study was to evaluate the use of a banana waste product as a carbon source for PHB production. PHB was extracted by acid methanolysis and detected by gas chromatography-mass spectrometry. Eleven bacterial strains with potential for PHB production were evaluated by in vitro fermentation in a culture broth containing fructose as the carbon source and limited nitrogen. A 22 central composite rotational design was applied to optimize the concentrations of banana juice and ammonium chloride needed to maximize the PHB-producing biomass concentration. The process was then carried out in a 3 L fed-batch fermentation system that included an initial stage of biomass growth. Banana juice was used as the carbon source and fructose pulses were added to maintain the test sugar concentrations of 30, 40, and 50 g/L. The control strain, Cupriavidus necator (ATCC 17699), produced 2.816 g/L of PHB, while productivity of the most promising isolate, C. necator (CR-12), was 0.495 g/L. Maximum biomass production was obtained using 5% banana juice and 2 g/L ammonium chloride. PHB production was not detected in fed-batch fermentations supplemented with 30 or 40 g/L of fructose, while the mean PHB production in fermentations with 50 g/L of fructose was 1.3 g/L.

Production of polyhydroxyalkanoates using dairy processing waste - A review

Bio-plastics are eco-friendly biopolymers finding tremendous application in the food and pharmaceutical industries. Bio-plastics have suitable physicochemical, mechanical properties, and do not cause any type of hazardous pollution upon disposal but have a high production cost. This can be minimized by screening potential bio-polymers producing strains, selecting inexpensive raw material, optimized cultivation conditions, and upstream processing. These bio-plastics specifically microbial-produced bio-polymers such as polyhydroxyalkanoates (PHAs) find application in food industries as packaging material owing to their desirable water barrier and gas permeability properties. The present review deals with the production, recovery, purification, characterization, and applications of PHAs. This is a comprehensive first review will also focus on different strategies adopted for efficient PHA production using dairy processing waste, its biosynthetic mechanism, metabolic engineering, kinetic aspects, and also biodegradability testing at the lab and pilot plant level. In addition to that, the authors will be emphasizing more on novel PHAs nanocomposites synthesis strategies and their commercial applicability.

Efficient bioconversion of sugarcane bagasse into polyhydroxybutyrate (PHB) by Lysinibacillus sp. and its characterization

In this study, Lysinibacillus sp. RGS was evaluated to synthesize polyhydroxybutyrate (PHB) from a broad range of pure carbon sources and residual sugars of chemically pretreated sugarcane bagasse (SCB) hydrolysates. Effects of supplementation of nutrients and various experimental variables to enhance PHB accumulation were investigated. Results of optimized parameters were identified as 48 h, 37 °C, pH 7; inoculums concentration (2.5% v/v) and shaking condition (100 rpm). Growth kinetics and bioprocess parameters of Lysinibacillus sp. using SCB hydrolysates with corn steep liquor (2%) accounted for the maximum cell growth (8.65 g/L) and PHA accumulation (61.5%) with PHB titer of (5.31 g/L) under optimal conditions. The produced biopolymer was studied by Fourier Transform Infrared (FTIR) spectroscopy and the results revealed the obtained to be PHB. Thus Lysinibaciluus sp. exhibits high potential in industrial scale manufacture of PHB using SCB as an inexpensive substrate.

Production and characterization of polyhydroxyalkanoates from industrial waste using soil bacterial isolates

Nowadays when conventional plastic is being looked as a menace, the possibility of it being replaced with polyhydroxyalkanoates (PHAs) which are biodegradable, environment friendly and biocompatible thermoplastics is not remote. PHAs are a fascinating group of biopolyesters stored within the cytoplasm of numerous bacterial cells as energy and carbon reserves. PHAs signify the best promising biological substitute to certain conventional petrochemical plastics which have wide range of applications in different industries such as biomedical sector, packaging, toners for printing, and adhesives for coating, etc. In the present study, PHAs producing bacterial strains were screened by Sudan black B staining and confirmed by Nile blue A staining. Out of forty bacterial strains showing positive results, six bacterial strains exhibited comparatively higher PHAs production. The highest PHAs producing bacterial strain was identified using 16s rRNA sequencing. Optimization of process parameters was performed by using one factor at a time (OFAT) approach. The isolated bacterium was able to synthesize PHAs when various agro-industrial wastes such as domestic kitchen waste, mixed fruit pulp, sugarcane molasses, and waste flour from bread factory were screened as a carbon substrate in the growth medium. The results showed accumulation of 44.5% PHAs of cell dry weight using domestic kitchen waste as carbon substrate. The characterization of biopolymers was performed using FTIR and XRD analysis. The commercial exploitation of results of this study may serve twin purposes of addressing the challenge of high production cost of PHAs being the major constraint in replacing petro-based plastics as well as address the problem of disposal of recurring domestic kitchen waste and other agro-industrial waste.

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The on-going SARS-CoV-2 causing COVID-19 discovered in December 2019, is responsible for a global pandemic. The virus belongs to the group of enveloped viruses containing linear, non-segmented, single stranded, positive sense strand RNA as genetic material. Already six different strains Coronaviruses are being reported to infect humans, however the seventh one is genetically similar to the SARS Coronavirus and termed as SARS-CoV-2. Specific crucial macromolecules such as membrane, nuclear, spike and enveloped proteins including HE esterase are present in the virus that interact with ACE2, APN, NEU-5, 9SC2 moiety of humans plays significant role in occurrence and transmission of the devastating disease. This review article summarizes the structure, histopathology, transmission of novel Coronavirus, its symptoms with preventive measures & currently prescribed drugs. Though various drugs and therapy have been administrated or implemented to restrict COVID-19, however it is imperative to develop an antidote against SARS-CoV-2 by the scientific or research community to save life.