Staphylococcal peroxidase inhibitor (SPIN): Investigation of the inhibitory N-terminal domain via a stabilizing disulfide insertion.

Staphylococcus aureus secretes an array of small proteins that inhibit key enzyme-catalyzed reactions necessary for proper function of the human innate immune system. Among these, the Staphylococcal Peroxidase Inhibitor, SPIN, blocks the activity of myeloperoxidase (MPO) and thereby disrupts the HOCl-generating system of neutrophils. Previous studies on S. aureus SPIN have shown that it relies on a C-terminal α-helical bundle domain to mediate initial binding to MPO, but requires a disordered N-terminal region to fold into a ß-hairpin conformation to inhibit MPO activity. To further investigate the structure/function relationship of SPIN, we introduced two cysteine residues into its N-terminal region to trap SPIN in its MPO-bound conformation and characterized the modified protein, which we refer to here as SPIN-CYS. Although control experiments confirmed the presence of the disulfide bond in SPIN-CYS, solution structure determination revealed that the N-terminal region of SPIN-CYS adopted a physically constrained series of lariat-like structures rather than a well-defined ß-hairpin. Nevertheless, SPIN-CYS exhibited a gain in inhibitory potency against human MPO when compared to wild-type SPIN. This gain of function persisted even in the presence of deleterious mutations within the C-terminal α-helical bundle domain. Surface plasmon resonance studies showed that the gain in potency arose through an increase in apparent affinity of SPIN-CYS for MPO, which was driven primarily by an increased association rate with MPO when compared to wild-type SPIN. Together, this work provides new information on the coupled binding and folding events required to manifest biological activity of this unusual MPO inhibitor.

Treatment challenges and outcomes of older patients with acute myeloid leukemia from India.

Globally, overall survival (OS) of older patients with AML continues to be suboptimal with very little data from India. In a multicenter registry analysis, we evaluated 712 patients with AML older than 55 years. Only 323 (45.3%) underwent further treatment, of which 239 (74%) received HMAs, and 60 (18%) received intensive chemotherapy (IC). CR was documented in 39% of those receiving IC and 42% after HMAs. Overall, 100 (31%) patients died within 60 days of diagnosis, most commonly due to progressive disease (47%) or infections (30%). After a median follow-up of 176 days, 228 (76%) of patients had discontinued treatment. At one year from diagnosis, 211 (65%) patients had died, and the median OS was 186 days (IQR, 137-234). Only 12 (3.7%) patients underwent stem cell transplantation. Survival was significantly lower for those older than 60 years (p < 0.001). Patients who died had a higher median age (p = .027) and baseline WBC counts (p = .006). Our data highlights suboptimal outcomes in older AML patients, which are evident from 55 years of age onwards, making it necessary to evaluate HMA and targeted agent combinations along with novel consolidation strategies to improve survival in this high-risk population.

Tailoring the Photophysical Properties of a Homoleptic Iron(II) Tetra N-Heterocyclic Carbene Complex by Attaching an Imidazolium Group to the (C∧N∧C) Pincer Ligand─A Comparative Study.

We here report the synthesis of the homoleptic iron(II) N-heterocyclic carbene (NHC) complex [Fe(miHpbmi)2](PF6)4 (miHpbmi = 4-((3-methyl-1H-imidazolium-1-yl)pyridine-2,6-diyl)bis(3-methylimidazol-2-ylidene)) and its electrochemical and photophysical properties. The introduction of the π-electron-withdrawing 3-methyl-1H-imidazol-3-ium-1-yl group into the NHC ligand framework resulted in stabilization of the metal-to-ligand charge transfer (MLCT) state and destabilization of the metal-centered (MC) states. This resulted in an improved excited-state lifetime of 16 ps compared to the 9 ps for the unsubstituted parent compound [Fe(pbmi)2](PF6)2 (pbmi = (pyridine-2,6-diyl)bis(3-methylimidazol-2-ylidene)) as well as a stronger MLCT absorption band extending more toward the red spectral region. However, compared to the carboxylic acid derivative [Fe(cpbmi)2](PF6)2 (cpbmi = 1,1'-(4-carboxypyridine-2,6-diyl)bis(3-methylimidazol-2-ylidene)), the excited-state lifetime of [Fe(miHpbmi)2](PF6)4 is the same, but both the extinction and the red shift are more pronounced for the former. Hence, this makes [Fe(miHpbmi)2](PF6)4 a promising pH-insensitive analogue of [Fe(cpbmi)2](PF6)2. Finally, the excited-state dynamics of the title compound [Fe(miHpbmi)2](PF6)4 was investigated in solvents with different viscosities, however, showing very little dependency of the depopulation of the excited states on the properties of the solvent used.

How Rigidity and Conjugation of Bidentate Ligands Affect the Geometry and Photophysics of Iron N-Heterocyclic Complexes: A Comparative Study.

Two iron complexes featuring the bidentate, nonconjugated N-heterocyclic carbene (NHC) 1,1'-methylenebis(3-methylimidazol-2-ylidene) (mbmi) ligand, where the two NHC moieties are separated by a methylene bridge, have been synthesized to exploit the combined influence of geometric and electronic effects on the ground- and excited-state properties of homoleptic FeIII-hexa-NHC [Fe(mbmi)3](PF6)3 and heteroleptic FeII-tetra-NHC [Fe(mbmi)2(bpy)](PF6)2 (bpy = 2,2'-bipyridine) complexes. They are compared to the reported FeIII-hexa-NHC [Fe(btz)3](PF6)3 and FeII-tetra-NHC [Fe(btz)2(bpy)](PF6)2 complexes containing the conjugated, bidentate mesoionic NHC ligand 3,3'-dimethyl-1,1'-bis(p-tolyl)-4,4'-bis(1,2,3-triazol-5-ylidene) (btz). The observed geometries of [Fe(mbmi)3](PF6)3 and [Fe(mbmi)2(bpy)](PF6)2 are evaluated through L-Fe-L bond angles and ligand planarity and compared to those of [Fe(btz)3](PF6)3 and [Fe(btz)2(bpy)](PF6)2. The FeII/FeIII redox couples of [Fe(mbmi)3](PF6)3 (-0.38 V) and [Fe(mbmi)2(bpy)](PF6)2 (-0.057 V, both vs Fc+/0) are less reducing than [Fe(btz)3](PF6)3 and [Fe(btz)2(bpy)](PF6)2. The two complexes show intense absorption bands in the visible region: [Fe(mbmi)3](PF6)3 at 502 nm (ligand-to-metal charge transfer, 2LMCT) and [Fe(mbmi)2(bpy)](PF6)2 at 410 and 616 nm (metal-to-ligand charge transfer, 3MLCT). Lifetimes of 57.3 ps (2LMCT) for [Fe(mbmi)3](PF6)3 and 7.6 ps (3MLCT) for [Fe(mbmi)2(bpy)](PF6)2 were probed and are somewhat shorter than those for [Fe(btz)3](PF6)3 and [Fe(btz)2(bpy)](PF6)2. [Fe(mbmi)3](PF6)3 exhibits photoluminescence at 686 nm (2LMCT) in acetonitrile at room temperature with a quantum yield of (1.2 ± 0.1) × 10-4, compared to (3 ± 0.5) × 10-4 for [Fe(btz)3](PF6)3.

Using Iron L-Edge and Nitrogen K-Edge X-ray Absorption Spectroscopy to Improve the Understanding of the Electronic Structure of Iron Carbene Complexes.

Iron-centered N-heterocyclic carbene compounds have attracted much attention in recent years due to their long-lived excited states with charge transfer (CT) character. Understanding the orbital interactions between the metal and ligand orbitals is of great importance for the rational tuning of the transition metal compound properties, e.g., for future photovoltaic and photocatalytic applications. Here, we investigate a series of iron-centered N-heterocyclic carbene complexes with +2, + 3, and +4 oxidation states of the central iron ion using iron L-edge and nitrogen K-edge X-ray absorption spectroscopy (XAS). The experimental Fe L-edge XAS data were simulated and interpreted through restricted-active space (RAS) and multiplet calculations. The experimental N K-edge XAS is simulated and compared with time-dependent density functional theory (TDDFT) calculations. Through the combination of the complementary Fe L-edge and N K-edge XAS, direct probing of the complex interplay of the metal and ligand character orbitals was possible. The σ-donating and π-accepting capabilities of different ligands are compared, evaluated, and discussed. The results show how X-ray spectroscopy, together with advanced modeling, can be a powerful tool for understanding the complex interplay of metal and ligand.

Surgical Cholecystectomy Score (SCS) for grading the difficulty of laparoscopic cholecystectomy.

BACKGROUND: Laparoscopic cholecystectomy (LC) is the standard of care for symptomatic gall stone disease. A good scoring system is necessary to standardize the reporting. Our aim was to develop and validate an objective scoring system, the Surgical Cholecystectomy Score (SCS) to grade the difficulty of LC. METHODS: The study was conducted in a single surgical unit at a tertiary care hospital in two phases from January 2017 to April 2021. Retrospective data was analysed and the difficulty of each procedure was graded according to the modified Nassar's scoring system. Significant preoperative and intraoperative data obtained was given a weightage score. In phase II, these scores were validated on a prospective cohort. Each procedure was classified either as easy, moderately difficult or difficult. STATISTICAL ANALYSIS: A univariate analysis was performed on the data followed by a multivariate regression analysis. Bidirectional stepwise selection was done to select the most significant variables. The Beta /Schneeweiss scoring system was used to generate a rounded risk score. RESULTS: Data of 800 patients was retrieved and graded. 10 intraoperative parameters were found to be significant. Each variable was assigned a rounded risk score. The final SCS range for intraoperative parameters was 0-15. The scoring system was validated on a cohort of 249 LC. In the final scoring, cut off SCS of > 8 was found to correlate with difficult procedures. Score of < 2 was equivalent to easy LC. A score between 2 and 8 indicated moderate difficulty. The area under ROC curve was 0.98 and 0.92 for the intraoperative score indicating that the score was an excellent measure of the difficulty level of LCs. CONCLUSION: The scoring system developed in this study has shown an excellent correlation with the difficulty of LC. It needs to be validated in different cohorts and across multiple centers further.

High-frequency stock market order transitions during the US-China trade war 2018: A discrete-time Markov chain analysis.

Statistical analysis of high-frequency stock market order transaction data is conducted to understand order transition dynamics. We employ a first-order time-homogeneous discrete-time Markov chain model to the sequence of orders of stocks belonging to six different sectors during the US-China trade war of 2018. The Markov property of the order sequence is validated by the Chi-square test. We estimate the transition probability matrix of the sequence using maximum likelihood estimation. From the heatmap of these matrices, we found the presence of active participation by different types of traders during high volatility days. On such days, these traders place limit orders primarily with the intention of deleting the majority of them to influence the market. These findings are supported by high stationary distribution and low mean recurrence values of add and delete orders. Further, we found similar spectral gap and entropy rate values, which indicates that similar trading strategies are employed on both high and low volatility days during the trade war. Among all the sectors considered in this study, we observe that there is a recurring pattern of full execution orders in the Finance & Banking sector. This shows that the banking stocks are resilient during the trade war. Hence, this study may be useful in understanding stock market order dynamics and devise trading strategies accordingly on high and low volatility days during extreme macroeconomic events.

Circulating serotypes and genotypes of dengue virus in North India: An observational study.

BACKGROUND OBJECTIVES: This study reports observation on circulating serotypes and genotypes of Dengue Virus in North India. METHODS: Serum samples were obtained from suspected cases of dengue referred to the virus diagnostic laboratory during 2014 to 2022. All samples were tested for anti-dengue virus IgM antibodies and NS1Ag by ELISA. NS1Ag positive samples were processed for serotyping and genotyping. RESULTS: Total 41,476 dengue suspected cases were referred to the laboratory of which 12,292 (29.6%) tested positive. Anti-Dengue Virus IgM antibodies, NS1Ag, both IgM and NS1Ag, were positive in 7007 (57.4%); 3200 (26.0%) and 2085 (16.0%) cases respectively. Total 762 strains were serotyped during 9-year period. DENV-1, DENV-2, DENV-3 and DENV-4 serotypes were found in 79 (10.37%), 506 (66.40%), 151 (19.82%) and 26 (3.41%) cases respectively. DENV-1, DENV-2 and DENV-3 were in circulation throughout. Total 105 strains were genotyped. Genotype IV of DENV-1 serotype was circulating till 2014 which was later replaced by genotype V. A distinct seasonality with increase in number of cases in post-monsoon period was seen. INTERPRETATION CONCLUSION: DENV-1, DENV-2 and DENV-3 were found to be in circulation in North India. Predominant serotype/genotype changed at times, but not at regular intervals.

Giant Cell Tumor of the Tendon Sheath of the Hand: Analysis of Factors Impacting Recurrence.

Background Giant cell tumors of the tendon sheath (GCTTS) of the hand are considered the second most common benign tumors of the hand after ganglion cysts. Excision biopsy is considered the standard treatment at present. They are notorious for having a very high rate of recurrence as given in many studies. Many factors are said to be associated with recurrence of the tumors. The goal of this study is to evaluate the long-term results of a series of 48 patients operated on at a single institute and to find out if there is any correlation between the proposed risk factors with recurrence. Methods A retrospective analysis was done in cases of GCTTS operated on between 2015 and 2021. The patients were invited for follow-up for a minimum of 2 years, and the patient files were reviewed. Further data were collected at follow-up including recurrence, range of movement, sensation, skin necrosis, scarring, and digital neuropathy. A data analysis was done. The correlation between the proposed risk factors and recurrence was calculated with the Pearson correlation coefficient. A p -value of less than 0.05 was considered statistically significant. Results During the 6 years, 48 patients were operated on. Recurrence was observed in eight patients (16%) at an average of 38.7 months from the time of surgery. Of the risk factors, tumors with satellite nodules and tumor adjacency to joint correlated significantly with recurrence. No complications were observed during follow-up. Conclusion GCTTS of the hand has a high propensity to recur. The presence of satellite nodules and proximity to interphalangeal joints are two important risk factors for recurrence. Magnification during surgery ensures complete excision of the tumor and reduces the chance of recurrence.

Utility of Fat Grafting in Chronic Wounds.

Introduction The history of wounds dates back to the evolution of mankind. Throughout the centuries, management modalities of wounds have undergone drastic changes. With the advent of technology, we have multiple options for wound care, but none of them can be called the gold standard of wound care. Autologous fat grafting (AFG) is one of the most routinely performed procedures in aesthetic surgery. Fat grafting has shown beneficial effects in the healing of wounds. The regenerative potential of autologous fat is contributed by the adipose-derived stem cells present within the stromal vascular fraction, which are capable of differentiating into multiple cell types. This study aims to analyze the usefulness of AFG in cutaneous wound healing. Materials and Methods This prospective, study was conducted in our institute between April 2021 and May 2023. Eighteen patients with nonhealing wounds were included in the study. For assessing wound healing all the patients were first managed with conventional dressing for 2 weeks before surgery. After routine preoperative workup, the procedure was performed under local anesthesia in most cases. Fat was harvested from the lower abdomen and after emulsification, was injected into the edge and floor of the ulcer. The dressing was changed on the third postoperative day and the outcome was assessed. Results Eighteen patients (M:F ratio 8:1), with a mean age of 35.61 ± 12. 64 years (range 10-65 years), were included in this study. The most common etiology was trauma (44%), others being postop infection (17%), veno-lymphatic ulcer (17%), burns (11%), insect bite (5%), and trophic ulcer (5%). Majority of the wounds (95%) healed without the need for any extra intervention. The mean period taken for complete wound healing was 5.05 weeks. Conclusion Complete wound healing was achieved in majority of the patients without any complications. We recommend the usage of AFG for nonhealing wounds, as the procedure is relatively simple and can be performed after basic training. Larger-scale randomized controlled trials should be conducted to prove their efficacy in the management of complicated wounds.

Reconsidering the discontinuation of M.Phil. programs in clinical psychology and psychiatric social work: An imperative for India's mental health future.

This viewpoint critically examines the New Education Policy (NEP) 2020's decision to discontinue M.Phil. programs in Clinical Psychology and Psychiatric Social Work in India. It explores the crucial roles these programs play in addressing the country's shortage of mental health professionals and evaluates the potential impact of this decision on mental healthcare. The article advocates for the necessity of these programs in maintaining the quality and accessibility of mental health services and calls for a reconsidered policy approach that balances educational reforms with the specialized needs of the mental health sector.

Protocol for enriching, isolating, and testing drug susceptibility of facultative anaerobic fungi.

Research on fungi under anaerobic conditions is limited but crucial for understanding their ecological and pathological impacts. Here, we present a protocol for enriching, isolating, and characterizing anaerobic fungi from environmental and clinical samples. We also describe steps for evaluating the anaerobic growth potential and drug susceptibility of fungal pathogens. This protocol can contribute to the need for initiating effective antifungal therapy to address and manage fungal infections or mycosis in oxygen-limited environments. For complete details on the use and execution of this protocol, please refer to Yadav et al.1.

Systemic inflammatory markers and their association with Alzheimer's disease: A cross-sectional analysis.

Aim: To investigate the possible role of systemic inflammatory markers (interleukin; IL-6, C-reactive protein; CRP, and albumin levels) in the development of Alzheimer's dementia (AD) and also find their association with the severity of disease. Material and Methods: It was a cross-sectional study. Patients with Alzheimer's dementia (AD) and vascular dementia (VaD) from outpatient settings in tertiary care hospitals and non-demented controls (NDC) were recruited from the community. Individuals aged 50 years and older (n = 110) were included. Serum levels of IL-6, CRP, and albumin levels in patients with AD, VaD, and NDC were measured. The clinical Dementia Rating Scale was used for staging the severity of dementia. Serum levels of IL-6, CRP, and serum albumin were compared in study subjects and also analyzed with the severity of dementia in dementia subgroups. Results: Our main finding was that serum levels of IL-6 were significantly elevated in patients with AD and VaD (7.79 and 6.60) as compared to NDC (2.98) (P < 0.001). No significant difference in CRP or albumin levels was observed between the three groups. Serum IL-6 and CRP showed a positive correlation with the severity of AD, though the correlation was significant only for IL-6 (r = 0.777). The serum albumin levels showed a statistically significant negative correlation with the severity of AD (r > 0.3 but <0.5). Conclusion: The study demonstrates a notable association between systemic inflammatory markers, particularly IL-6, and the severity of AD, indicating their potential role in its pathogenesis. These findings suggest that targeting these markers could offer new insights into therapeutic strategies for AD.

Isolated Myocysticercosis of Pectoralis Major: A Rare Case.

Isolated myocysticercosis is a neglected tropical disease and a rare diagnosis, with only a handful of cases being reported in the literature. It is highlighted that recently, it has not only been limited to endemic regions but also persists globally due to widespread migration from endemic regions. We present a case of isolated myocysticercosis of the right pectoralis major without neurological involvement in a non-pork-eater. High-resolution ultrasonography is an effective method of diagnosis. Anti-helmintic drugs are effective treatment options; if not responding, surgical excision is the management of choice. Ultrasound-guided excision is a better treatment modality to prevent complications.

Effectiveness of Injectable Platelet-Rich Fibrin in the Treatment of Oral Lichen Planus: A Systematic Review and Meta-Analysis.

Oral lichen planus (OLP) is a chronic inflammatory condition affecting the oral mucosa. The current review investigated the potential effectiveness of injectable platelet-rich fibrin (i-PRF) as a treatment for OLP when compared to other interventions. The current review adhered to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A comprehensive search strategy was implemented across databases such as PubMed, Embase, Scopus, Web of Science, CINAHL, and Google Scholar. The search utilized a combination of Boolean operators (AND, OR) and Medical Subject Headings (MeSH) terms to capture relevant studies. Comparative clinical studies focusing on i-PRF as a treatment for OLP and other interventions were included. Outcomes assessed were pain, surface area of lesions, and patient satisfaction. Review Manager 5.4 was used for statistical analysis. The Risk of Bias 2.0 (RoB 2.0) tool was used to assess the methodological quality of the studies. Three studies were included for the final analysis. The findings indicated that both the i-PRF and comparison treatment groups demonstrated reductions in pain and lesion size. The post-treatment Visual Analogue Scale (VAS) scores showed a decrease in pain intensity, and there was an improvement in lesion extension in the i-PRF-treated sites. The results also revealed increased patient satisfaction with i-PRF treatment. Adverse effects were not reported or specified in the included studies. Quantitative analysis for pain (VAS) showed a mean difference of 0.38 (95% CI: 0.63-1.40), but there was no significant difference between the i-PRF and control groups at p=0.46. Though intragroup differences showed statistically significant differences between pre and post intervention, intergroup differences were not significant for any of the assessed outcomes. The findings from this study suggest that i-PRF holds promise as a potential treatment for OLP. The use of i-PRF resulted in pain reduction, lesion size improvement, and increased patient satisfaction. However, it is important to consider the limitations of the included studies, such as variability in study designs, small sample sizes, and the limited number of studies.

Comparison of Buccal and Lingual-Based Triangular Flap During Mandibular Third Molar Extraction for Reducing Postoperative Complications: A Randomized Controlled Trial.

Background: Surgical removal of the mandibular third molar requires reflection of the mucoperiosteal flap. Several studies have suggested different varieties and innovative designs for flap reflection. We have designed a randomized controlled trial (RCT) to check the feasibility of two flap designs: lingual-based triangular flap (LBTF) and buccal-based triangular flap (BBTF) by calculating the duration of surgery and evaluating postoperative complications such as pain, swelling, and trismus. Materials and Method: It was a non-inferiority parallel-group RCT. The trial was registered in the Control Trial Register of India (CTRI/2021/10/037182) and was performed according to Consolidated Standards of Registered Trial (CONSORT) guidelines. Intraoperative surgery time and postoperative pain, swelling, and trismus were measured and analyzed by a two-sample t test. The Chi-square test was used to measure gender distribution in the study. Result: Of the total of 88 required subjects, gender distribution and performed surgical time were statistically insignificant with a p-value of 0.76 and 0.48, respectively. The pain was significantly higher in the LBTF group in the 5th and 7th postoperative days with a p-value of 0.02 and 0.028. The swelling was statistically higher during all the follow-ups except for the 28th day in the LBTF group with values of 0.006, 0.002 and 0.003, respectively. There was no significant difference in inter-incisional distance (IID) between the groups during postoperative check-ups. Conclusion: LBTF shows no edge over BBTF during mandibular third molar disimpaction.

Exploring the diversity of vaginal microbiota between healthy women and cervical cancer patients in India.

Introduction. Cervicovaginal diversity has been reported as a predictive biomarker for cervical cancer risk. We recently reported the bio-therapeutic potential of vaginal probiotics from healthy Indian women against vaginal pathogens, isolated from the invasive cervical cancer (ICC) patients.Gap Statement. The cervicovaginal microflora from cervical cancer patients has not yet been reported from Indian population.Aim. The present study aimed at comparing the cervicovaginal microbiome between healthy controls (HC) and ICC patients from the Indian population.Methodology. In total, 30 vaginal swabs (15 from HC and 15 from ICC) were subjected to 16S rRNA gene sequencing. Alpha diversity was evaluated by Shannon and Chao1 index; and beta diversity by principle coordinate analysis (PCoA) of weighted and unweighted UniFrac distances. The relative abundance of the microbial taxa was done according to linear discriminant analysis effect size (LEfSe).Results. Predominance of Staphylococcus spp. in ICC and Lactobacillus gasseri in HC groups was observed. Alpha-diversity was found to be higher in ICC as compared to HC but was statistically non-significant. LEfSe analysis revealed Bacteroides fragilis and Escherichia coli as the marker genera in ICC with a marked decrease in Lactobacillus sp. Contrarily, in HC, L. gasseri, L. iners and L. fermentum were found to be abundant.Conclusion. Differences in the vaginal microbiome between healthy and ICC women could help in the early prediction of cervical cancer risk and thus in designing prevention strategies.

Development and techno-economic analysis of Grewia biopolymer-based dual coagulant system for wastewater treatment at pilot scale.

Use of Grewia biopolymer as a natural coagulant aid was explored in a dual-coagulant system (conventional coagulant + biopolymer) for wastewater treatment. Such use not only improved turbidity removal efficiency over a wide pH range (5-9) but also helped reducing the concentration demand of inorganic coagulants by 25-50 %. Response surface methodology was employed for investigating the interaction between factors (initial pH, coagulant, and biopolymer concentration) affecting coagulation/flocculation of aqueous laterite suspension, and process optimization for more than 80 % turbidity removal in the desired final pH range (6-7). Mechanisms potentially involved in coagulation/flocculation using biopolymer was elucidated. Techno-economic assessment indicated the feasibility of pilot-scale production of the biopolymer and its use in wastewater treatment. This study demonstrates that Grewia biopolymer has the potential to be used as a coagulant aid and will help researchers select appropriate markets for further cost reduction and successful implementation of biopolymer-based wastewater treatment.

Effects of particle size on the pretreatment efficiency and subsequent biogas potential of polylactic acid.

The fragmentation of bioplastics (BPs) before pretreatment and anaerobic digestion is conducted for higher efficiency; however, based on the literature, the size reduction varies widely. In this study, initially, various combinations of thermal-alkaline pretreatments were applied at different strengths to the polylactic acid (PLA) in three groups (<0.5, 0.5 < size < 1.0, and 1.0 < size < 2.0 mm). After pretreatment, the solubilization of PLA was increased to 11.5-40.0 % using alkaline dosage and temperature ranging from 50 to 200 g OH-/kg BP, 60-100 °C, respectively, in a 1-10 h timeframe. The results were statistically proved using a 3D response surface graph, where the pretreatment was more effective for smaller particle sizes. The reduction in particle size also increased the CH4 production, which was more pronounced at the strong pretreatment (24 % increment vs. 10-15 %). Computed results indicated 44-86 % conversion of pretreated PLA particles to CH4, supported by Fourier transform infrared spectroscopy analysis, especially focusing on the intensity of -OH bands.