Biopolishing Exhaust Processes for Cotton Knits After Mercerization

The biopolishing step follows the removal of knitting oils and waxes through a high-temperature scour and the optional mercerization of cotton cellulosic surfaces. Acid cellulase derived from Trichoderma reesei is dosed at 0.5–3.0% o.w.f. in soft-flow overflow dyeing machines with nominal loading capacities between 400 kg and 1200 kg. The process bath is buffered with sodium acetate/acetic acid to maintain pH 4.8–5.2, and circulation speed is set so that fabric turnover occurs every 1.5–3.0 min. Exhaustion at 50–55°C for 30–60 min removes surface fuzz and immature fiber ends from single jersey, interlock, and pique constructions. The enzyme is deactivated by raising bath pH to 10.0–10.5 with soda ash or by increasing temperature above 80°C for 10 min. This deactivation is critical because residual enzyme activity in wet storage can continue hydrolyzing cotton and cause through-thickness tensile loss in storage cartons. Finished knitwear is tested for pilling resistance according to ASTM D3512 after 30 min of random tumble, and a pilling rating below 4 triggers a re-processing decision. Tensile retention is controlled by ASTM D5034-09(2017) grab testing, with a production control limit of ≤10% strength loss relative to the scoured blank. Dimensional stability is assessed by ISO 6330 and ISO 5077, which separate enzymatic weight loss from mechanical shrinkage. Regulatory compliance for the biopolished article falls under ZDHC MRSL v3.1 and the bluesign system criteria for enzyme preparations, while the residual monomer and solvent profile is screened under Oeko-Tex Standard 100 Annex 4.

Process conflicts arise when the fabric contains elastane or cationic-dyeable polyester blends, because the acid buffer at pH 4.8 can attack polyurethane filaments during extended dwell times. In those cases, neutral cellulase at pH 6.0–7.0 is substituted, with the temperature set at 50–60°C and the duration limited to 40 min. Overdosing above 3.0% o.w.f. on lightweight knits below 140 g/m² produces excessive weight loss and seam slippage. The terminal article is a de-pilled, softened cotton knit for underwear, T-shirts, and infant apparel.

In denim finishing lines where pumice stone dust creates respiratory exposure and machine wear concerns, neutral cellulase eliminates the need for pumice while preserving surface contrast on indigo-dyed twill. Garment processing is carried out in front-loading drum washers with programmable inverter drives and drum volumes between 200 L and 1200 L; the liquor ratio is held at 1:6–1:12 with a neutral cellulase dose of 0.7–3.0% o.w.f. The desizing step uses an amylase at 60–70°C for 10–20 min before the cellulase bath is set at pH 6.0–7.5 with a phosphate or acetic acid buffer. Abrasion is developed at 45–65°C for 20–60 min, depending on desired contrast level and fabric weight; heavier ringspun denim above 14 oz/yd² typically requires the upper end of the dosage and time ranges. Indigo redeposition is the main process conflict: hydrolyzed cotton microfibrils can adsorb indigo from the bath and produce a grey cast on pockets and seams. Anti-backstaining agents, generally nonionic ethoxylates or modified polyester dispersants, are added at 0.5–1.5 g/L to suppress redeposition without interfering with enzyme activity. The enzyme is stopped by raising bath pH to 10.0 with sodium carbonate or by increasing temperature to 80°C for 10 min, after which a two-stage rinse removes dissolved indigo. Final garments are evaluated for abrasion according to ASTM D3885 and tensile strength according to ASTM D5034, with a maximum acceptable tensile loss of 10–15% depending on customer specification. Compliance for the enzyme preparation is documented under REACH (EC) No 1907/2006 Annex VIII safety data sheet requirements and ZDHC MRSL v3.1; the finished denim must not show APEO residues above the detection limits of ISO 18218-1.

What Limits Cellulase Tenacity in Liquid Detergent Matrices at pH 8.5?

Liquid cellulase preparations containing endoglucanase-rich fermentation broths are compounded into heavy-duty liquid laundry detergents at 0.2–0.8% w/w of the finished formulation. The enzyme is standardized to 5000–10000 ECU/g and is active on cotton fibrils after the wash liquor dilutes the product to roughly 1:200. The formulation pH is maintained between 8.0 and 9.5 with monoethanolamine citrate or sodium carbonate buffers, while boric acid or sodium borate is used at 1.0–3.0% w/w to stabilize the cellulase during storage. Calcium chloride or calcium formate is introduced at 0.1–0.5% w/w because the catalytic domain of the enzyme requires a divalent cation bridge for thermal stability. Anionic surfactants such as linear alkylbenzene sulfonate and alcohol ether sulfate are kept in the 15–30% w/w range; above this level, the surfactant-enzyme interface denatures the cellulase and produces visible precipitation after 4-week storage at 37°C. Protease compatibility is the central formulation constraint: in formulations where protease exceeds 0.4% w/w active enzyme preparation, cellulase proteolysis is minimized by using a hydrophobic core variant or by coating the cellulase in a polymer dispersion. Wash performance is tested according to ASTM D4265-14 for multi-stain cool water cleaning and IEC 60456 for machine wash comparisons. Color retention and pilling are measured according to AATCC 61 and ASTM D3512 respectively. The detergent label and ingredient declaration must comply with EU Detergents Regulation (EC) No 648/2004 Annex VII, and any imported enzyme preparation must be documented for REACH (EC) No 1907/2006 registration. The finished article relevant to this application is a clear or opaque liquid detergent, including unit-dose pouches with water activity below 0.8, where cellulase removes fibrillar fuzz and restores original cotton appearance at wash temperatures of 20–40°C.

Recycled-Fiber Deinking and Schopper-Riegler Drainage Response to Neutral Cellulase

Continuous repulping of mixed office waste requires that enzyme addition be synchronized with the pulper charge rather than added as a post-refining corrective. Neutral cellulase is dosed at 0.05–0.3% on oven-dry fiber mass in a high-consistency hydrapulper operating at 12–15% consistency, pH 6.5–7.5, and 45–60°C. Retention time in the pulper ranges from 30–60 min, after which the stock is diluted and screened. The enzyme cleaves cellulosic fines and toner-fiber bonds, allowing ink particles to detach and float in a subsequent deinking cell. Process control is based on Schopper-Riegler drainage values measured under ISO 5267-1; a target reduction of 3–8 °SR relative to the control batch confirms drainage improvement without over-hydrolysis. Brightness is measured under ISO 2470, and residual ink is quantified under TAPPI T 213 or equivalent ERIC methodology. The main risk is excessive cellulase action on long-fiber fractions: if the enzyme dose exceeds 0.4% on oven-dry fiber or retention time exceeds 90 min, the degree of polymerization falls and the tensile index measured under ISO 1924-2 drops below the target for tissue or copy paper grades. Mill-scale equipment for this application includes a continuous drum pulper or high-consistency batch pulper followed by a dissolved-air flotation cell and a disc refiner; enzyme injection is made through a dosing ring in the pulper dilution line to avoid localized concentration spikes. Regulatory compliance for food-contact tissue made from recycled fiber includes FDA 21 CFR 176.170 for paper and paperboard in contact with aqueous and fatty foods, BfR Recommendation XXXVI for paper for food contact, and REACH (EC) No 1907/2006 for the enzyme preparation. The terminal products are deinked market pulp, tissue base sheet, and recycled newsprint.

When High-Solids Lignocellulosic Slurries Above 20% Dry Matter Enter Enzymatic Hydrolysis

Separate hydrolysis and fermentation configurations using steam-exploded or dilute-acid-pretreated corn stover are constrained by two thresholds: the dry matter content at the start of hydrolysis and the cellobiose concentration at 24 h. Cellulase from Trichoderma reesei, supplemented with β-glucosidase, is dosed at 5–30 FPU/g glucan; the slurry pH is adjusted to 4.8–5.2 with ammonium hydroxide, and the hydrolysis temperature is maintained at 48–55°C for 72–120 h. At solids above 20% dry matter, the mixing behavior shifts from free-flowing to pseudo-plastic, and mass transfer becomes the rate-limiting factor rather than enzyme-substrate binding. Horizontal reactors with intermeshing helical impellers are used instead of stirred tanks, and fed-batch addition of pretreated biomass in 4–6 increments during the first 12–18 h prevents the yield loss caused by initial viscosity peaks. The carbohydrate composition of the feedstock is analyzed according to NREL/TP-510-42629, and total solids are measured under ASTM E1756-08. Inhibitors released during pretreatment, including acetic acid at 1–4 g/L, furfural, and 5-hydroxymethylfurfural, reduce cellulase adsorption on cellulose; washing or detoxification of the pretreated slurry is required when combined inhibitor concentration exceeds the tolerance of the production strain. The enzyme hydrolysis is terminated by cooling to 4°C or by separating the hydrolysate through a filter press, after which the glucose syrup is fermented to ethanol. Conversion efficiency is calculated as glucose yield over theoretical glucan content, with published data for this configuration showing broad variability from 60% to 85% depending on pretreatment severity, solids profile, and enzyme loading. Compliance for export of the resulting cellulosic ethanol falls under the EU Renewable Energy Directive II (RED II) greenhouse gas calculation methodology and the ASTM E1756-08 solids determination; enzyme documentation must conform to REACH (EC) No 1907/2006 for industrial enzymes in closed systems.

Before pelleting, dry cellulase formulations are introduced into the mash conditioner at the point where steam injection raises the meal temperature to 70–85°C. The inclusion rate in corn-soybean meal diets is 100–400 g/t of finished feed for a dry product standardized to ≥1000 U/g endoglucanase activity, while barley-wheat diets for broilers require the upper half of the range due to higher mixed-linked β-glucan and arabinoxylan content. The enzyme hydrolyzes soluble non-starch polysaccharides that increase digesta viscosity in monogastric animals; this action improves contact between pancreatic enzymes and the feed matrix, but published data for specific metabolizable energy shifts are limited and vary across dietary fiber sources. Liquid cellulase preparations are applied post-pelleting through a vacuum coater to avoid thermal deactivation above 80°C; this preserves activity but requires a uniform spray pattern and a re-drying step when the product exceeds 0.5% w/w moisture addition. In a ring die pellet mill, the conditioner retains the meal for 30–90 s, and die temperature in the compression zone is monitored because cellulase denaturation occurs quickly above 85°C. The finished pelleted broiler or swine grower-finisher feed is tested for enzyme activity recovery using the analytical method prescribed in the zootechnical additive authorization dossier. The zootechnical additive must be authorized under EU Regulation (EC) No 1831/2003 before placing on feed. Imported dry enzyme premixes are documented under GHS classification and REACH (EC) No 1907/2006 for protein dust sensitization, and the final compound feed must meet the maximum residue limits governing agricultural contaminants where applicable.