Modeling of poly-ß-hydroxybutyrate production by Bacillus subtilis and its use for feed-forward bioreactor studies.

Successful scale-up of Bacillus subtilis culture for poly-ß-hydroxybutyrate (PHB) production was performed in 5-l stirred-tank reactor using batch, fed-batch, and two-stage culture strategies. The kinetics of biomass production, substrate consumption, and PHB production were established in the stirred tank bioreactor in all the studies. A mathematical model was developed to investigate the role of limiting substrate on overall culture metabolism. A fed-batch strategy was predicted on the basis of computer simulations, for maximum PHB production. This was performed by extrapolation of batch model for predicting the feeding rate and suitable time of feeding. Substrate inhibition was studied and the substrate inhibition terms were incorporated in the model. The maximum cell biomass concentration in batch culture (24 h) and fed-batch culture (30 h) was 1.79 ± 0.03 g/l on dry cell weight (DCW) basis and 1.66 ± 0.050 g/l on DCW basis and the corresponding PHB content was 68.71% and 85.54% of DCW, respectively. Glucose was found to be the major limiting nutrient during the bioreactor culture. A two-stage culture, where cells were first grown in stage I in LBG media containing excess carbon and thereafter in stage II in OM media, showed biomass production of 1.95 ± 0.045 g/l at 4 h and PHB production of 93.33% of DCW at 16 h. A 9% increase in growth and 25% increase in PHB yield were obtained using two-stage culture with computer-simulated feeding strategy in the 5 l reactor. Oxygen limitation was overcome in modified two-stage culture to obtain a PHB production of 98% at 30 h. KEY POINTS: • Polyhydroxybutyrate production was studied in a 5-l stirred-tank bioreactor using HPLC • Mathematical model-assisted fed-batch strategy was implemented in bioreactor • Two-stage fed-batch cultivation was implemented and PHB production was 93% of dry weight in Gram-positive bacteria.

Investigating microcrystalline cellulose crystallinity using Raman spectroscopy.

Microcrystalline cellulose (MCC) is a semi-crystalline material with inherent variable crystallinity due to raw material source and variable manufacturing conditions. MCC crystallinity variability can result in downstream process variability. The aim of this study was to develop models to determine MCC crystallinity index (%CI) from Raman spectra of 30 commercial batches using Raman probes with spot sizes of 100 µm (MR probe) and 6 mm (PhAT probe). A principal component analysis model separated Raman spectra of the same samples captured using the different probes. The %CI was determined using a previously reported univariate model based on the ratio of the peaks at 380 and 1096 cm-1. The univariate model was adjusted for each probe. The %CI was also predicted from spectral data from each probe using partial least squares regression models (where Raman spectra and univariate %CI were the dependent and independent variables, respectively). Both models showed adequate predictive power. For these models a general reference amorphous spectrum was proposed for each instrument. The development of the PLS model substantially reduced the analysis time as it eliminates the need for spectral deconvolution. A web application containing all the models was developed. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10570-021-04093-1.

Correlating Single Crystal Structure, Nanomechanical, and Bulk Compaction Behavior of Febuxostat Polymorphs.

Febuxostat exhibits unprecedented solid forms with a total of 40 polymorphs and pseudopolymorphs reported. Polymorphs differ in molecular arrangement and conformation, intermolecular interactions, and various physicochemical properties, including mechanical properties. Febuxostat Form Q (FXT Q) and Form H1 (FXT H1) were investigated for crystal structure, nanomechanical parameters, and bulk deformation behavior. FXT Q showed greater compressibility, densification, and plastic deformation as compared to FXT H1 at a given compaction pressure. Lower mechanical hardness of FXT Q (0.214 GPa) as compared to FXT H1 (0.310 GPa) was found to be consistent with greater compressibility and lower mean yield pressure (38 MPa) of FXT Q. Superior compaction behavior of FXT Q was attributed to the presence of active slip systems in crystals which offered greater plastic deformation. By virtue of greater compressibility and densification, FXT Q showed higher tabletability over FXT H1. Significant correlation was found with anticipation that the preferred orientation of molecular planes into a crystal lattice translated nanomechanical parameters to a bulk compaction process. Moreover, prediction of compactibility of materials based on true density or molecular packing should be carefully evaluated, as slip-planes may cause deviation in the structure-property relationship. This study supported how molecular level crystal structure confers a bridge between particle level nanomechanical parameters and bulk level deformation behavior.

Distribution of airborne microbes and antibiotic susceptibility pattern of bacteria during Gwalior trade fair, Central India.

BACKGROUND/PURPOSE: Research into the distribution of bioaerosols during events associated with huge groups of people is lacking, especially in developing countries. The purpose of this study was to understand the distribution pattern of bioaerosols during an annual trade fair in the historical city of Gwalior, central India, a very important historical fair that was started by the King of Gwalior Maharaja Madho Rao in 1905. METHODS: Air samples were collected from six different sites at the fair ground and three different sites in a residential area before/during/after the fair using an impactor sampler on microbial content test agar and rose bengal agar for total bacteria and fungi, respectively. The representative strains of bacteria and fungi were further identified and selected bacterial strains were subjected to antibiotic susceptibility testing according to US Clinical and Laboratory Standards Institute (CLSI) guidelines. RESULTS: The bacterial bioaerosol count [colony-forming units (CFU)/m(3)] at fair sites was found to be 9.0 × 10(3), 4.0 × 10(4), and 1.0 × 10(4) before the start of the fair, during the fair, and after the fair, respectively. The fungal bioaerosol count at fair sites was 2.6 × 10(3) CFU/m(3), 6.3 × 10(3) CFU/m(3), and 1.7 × 10(3) CFU/m(3) before the fair, during the fair, and after the fair, respectively. Bacterial/fungal bioaerosols during-fair were increased significantly from the bacterial/fungal bioaerosols of the before-fair period (p < 0.05); they were also significantly higher than the bacterial/fungal bioaerosols at non-fair sites during the event (p < 0.0001). The proportion of antibiotic-resistant bacteria over the fair ground was significantly increased during-fair and was still higher in the after-fair period. Methicillin-resistant staphylococci (MRS) were also reported at the fair ground. CONCLUSION: The study indicates significantly higher bacterial and fungal bioaerosols during the fair event. Therefore, further research is needed to explore the health aspects and guidelines to control microbial load during such types of events.

Antibacterial activity of actinomycetes isolated from different soil samples of Sheopur (A city of central India).

The main objective of the present study was isolation, purification, and characterization of actinomycetes from soil samples, having antimicrobial activity against 12 selected pathogenic strains. Soils samples were taken from different niche habitats of Sheopur district, Madhya Pradesh, India. These samples were serially diluted and plated on actinomycete isolation agar media. Potential colonies were screened, purified, and stored in glycerol stock. Isolates were morphologically and biochemically characterized. These isolates were subjected to extraction for production of the antibacterial compound. Antibacterial activity and Minimum Inhibitory Concentration (MIC) of the purified extract of isolates were evaluated. Totally 31 actinomycete isolates were tested for antagonistic activity against 12 pathogenic microorganisms. Isolates AS14, AS27, and AS28 were highly active, while AS1 showed less activity against the pathogenic microorganisms. Isolate AS7 exhibited the highest antagonistic activity against Bacillus cereus (24 mm) and AS16 showed the highest activity against Enterococcus faecalis (21 mm). MIC was also determined for actinomycete isolates against all the tested microorganisms. MIC of actinomycete isolates was found to be 2.5 mg/ml against Shigella dysenteriae, Vancomycin-resistant enterococci, and Klebsiella pneumoniae, and was 1.25 mg/ml for Staphylococcus saprophyticus, Streptococcus pyogenes, Staphylococcus epidermidis, Methicillin-resistant Staphylococcus, Bacillus cereus, Staphylococcus xylosus, Methicillin-resistant Staphylococcus aureus, Enterococcus faecalis, and Staphylococcus aureus. All actinomycetes isolates showed antibacterial activity against S. aureus, while they showed less activity against S. dysenteriae. These isolates had antibacterial activity and could be used in the development of new antibiotics for pharmaceutical or agricultural purposes.